It is a misunderstanding of Josephus to read his works as if they were a chronicle of facts happily shedding light on the background to the rise of Christianity.
To get the most reliable data from Josephus it is better to first study his works in the context of other historical writings of his day. In that context it is evident that Josephus is writing a "tragic history" -- a narrative that he presents as a tragedy, a form of narrative with which his Greco-Roman audience was familiar. As a tragedy Josephus seeks to elicit his audience's sympathy and tears by using all of his rhetorical skills to portray graphic suffering and misfortune. In
War Josephus opens with the proud Herod whose hubris is brought low by the misfortunes that follow. The audience knows how the story ends and that knowledge only adds to their awareness of irony and the tragic of each scene. The irony of temple slaughter at Passover time would have been as clear to Roman as to Jewish readers: Passover was known to have been the festival of liberation.
Josephus has an abundance of "robbers" or "bandits" who polluted the temple -- just as per Jeremiah 7:11
“Has this house, which is called by my name, become a den of robbers in your eyes?”
The same motif was drafted by Tacitus (Hist. 3.71-72):
Since the city’s foundation, this was the most deplorable and disgraceful event. ... Facing no foreign enemy, and with the Gods propitious if only our behaviour permitted, the seat of Iuppiter Optimus Maximus, founded by our ancestors with auspices as pledge of imperium ... was destroyed by the madness of our own principes [those contending for rule].
Josephus blends Jewish and Greek literary motifs in his tragic narration. For details see Steve Mason, pp. 114-121.
Omens and prophecies:
Tacitus and Suetonius both speak of omens and prophecies preceding a change of ruler -- a motif that was near universal in ancient historiography.
Tacitus:
78 1 After Mucianus had spoken, the rest became bolder; they gathered about Vespasian, encouraged him, and recalled the prophecies of seers and the movements of the stars. Nor indeed was he wholly free from such superstitious belief, as was evident later when he had obtained supreme power, for he openly kept at court an astrologer named Seleucus, whom he regarded as his guide and oracle. Old omens came back to his mind: once on his country estate a cypress of conspicuous height suddenly fell, but the next day it rose again on the selfsame spot fresh, tall, and with wider expanse than before. This occurrence was a favourable omen of great significance, as the haruspices all agreed, and promised the highest distinctions for Vespasian, who was then still a young man. At first, however, the insignia of a triumph, his consulship, and his victory over Judea appeared to have fulfilled the promise given by the omen; yet after he had gained these honours, he began to think that it was the imperial throne that was foretold. Between Judea and Syria lies Carmel: this is the name given to both the mountain and the divinity. The god has no image or temple — such is the rule handed down by the fathers; there is only an altar and the worship of the god. When Vespasian was sacrificing there and thinking over his secret hopes in his heart, the priest Basilides, after repeated inspection of the victim's vitals, said to him: "Whatever you are planning, Vespasian, whether to build a house, or to enlarge your holdings, or to increase the number of your slaves, the god grants you a mighty home, limitless bounds, and a multitude of men." This obscure oracle rumour had caught up at the time, and now was trying to interpret; nothing indeed was more often on men's lips. It was discussed even more in Vespasian's presence — for men have more to say to those who are filled with hope. The two leaders now separated with clear purposes before them, Mucianus going to Antioch, Vespasian to Caesarea. Antioch is the capital of Syria, Caesarea of Judea.39
Suetonius
5 1 While Otho and Vitellius were fighting for the throne after the death of Nero and Galba, he began to cherish the hope of imperial dignity, which he had long since conceived because of the following portents.
2 On the suburban estate of the Flavii an old oak tree, which was sacred to Mars, on each of the three occasions when Vespasia was delivered suddenly put forth a branch from its trunk, obvious indications of the destiny of each child. The first was slender and quickly withered, and so too the girl that was born died within the year; the second was very strong and long and portended great success, but the third was the image of a tree. Therefore their father Sabinus, so they say, being further encouraged by an inspection of victims, announced to his mother that a grandson had been born to her would be a Caesar. But she only laughed, marvelling that her son should already be in his dotage, while she was still of strong mind.
3 Later, when Vespasian was aedile, Gaius Caesar, incensed at his neglect of his duty of cleaning the streets, ordered that he be covered with mud, which the soldiers accordingly heaped into the bosom of his purple-bordered toga; this some interpreted as an omen that one day in some civil commotion his country, trampled under foot and forsaken, would come under his protection and as it were into his embrace.
4 Once when he was taking breakfast, a stray dog brought in a human hand from the cross-roadsc and dropped it under the table.14 Again, when he was dining, an ox that was ploughing shook off its yoke, burst into the dining-room, and after scattering the servants, fell at the very feet of Vespasian as he reclined at table, and bowed its neck as if suddenly tired out. A cypress tree, also, on his grandfather's farm was torn up by the roots, without the agency of any violent storm, and thrown down, and on the following day rose again greener and stronger than before.
5 He dreamed in Greece that the beginning of good fortune for himself and his family would come as soon as Nero had a tooth extracted; and on the next day it came to pass that a physician walked into the hall15 and showed him a tooth which he had just then taken out.
6 When he consulted the oracle of the god of Carmel in Judaea, the lots were highly encouraging, promising that whatever he planned or wished however great it might be, would come to pass; and one of his high-born prisoners, Josephus by name, as he was being put in chains, declared most confidently that he would soon be released by the same man, who would then, however, be emperor. 7 Omens were also reported from Rome: Nero in his latter days was admonished in a dream to take the sacred chariot of Jupiter Optimus Maximus from its shrine to the house of Vespasian and from there to the Circus. Not long after this, too, when Galba was on his way to the elections which gave him his second consulship, a statue of the Deified Julius of its own accord turned towards the East; and on the field of Betriacum, before the battle began, two eagles fought in the sight of all, and when one was vanquished, a third came from the direction of the rising sun and drove off the victor.
That "ambiguous prophecy" we read about in Josephus was but one of a raft of signs that were said to have preceded the rise of a new dynasty to the emperorship.
Needless to say such signs were as a rule "discovered" as a rule in hindsight. They were recorded as if they preceded the events, but realistically I think we can say a lot of imaginative hindsight has gone into writing about what "so many" people all observed before the event.
(Good idea to keep this in mind next time we hear someone say stories would not be made up if there were living witnesses who could contradict them.)
Josephus's prophecy sits well with the portents described by other historians of his time. It was par for the course to write about "ambiguous oracles" predicting a dramatic change in rulers. Should we privilege Jewish historians as being more likely to "tell nothing but the historical facts" any more than the Roman and Greek ones?
Josephus's surrender
Josephus rightly distrusted Vespasian when he called upon him to surrender. Eventually when Josephus did come out from hiding in his cave he was promptly put in chains and destined to be sent by Vespasian to Nero. Josephus had every reason to fear for his fate: last time he had traveled to see Nero he had nearly drowned in a shipwreck and then only won his case by the good grace of Nero's wife -- whom Nero had since had executed. For Josephus to appear before Nero a second time as a war captive would have meant certain death.
Josephus, we can presume, had every motive to appeal fervently to Vespasian to avoid that fate.
We don't know what words Josephus used to extricate himself over the year he was held in chains.
But whatever happened, whatever arguments were plied, after Vespasian was indeed proclaimed emperor -- this "upstart" from a less than noble family -- a prediction by an exotic eastern priest" surely had propaganda value. (Mason, p. 125)
Vespasian needed all the propaganda support he could get. He had not conquered a foreign nation but merely put down an internal revolt -- not the sort of action that was deserving of a Roman Triumph. But Vespasian went overboard and built up his action in Judea as equivalent of the crushing of a mighty enemy nation and exploited his son Titus's spoils to proclaim himself an emperor fully deserving of a Triumph -- and if he were so mighty and deserving, then who could criticise his rise to power despite his family background.
Tacitus and Suetonius had Vespasian's propaganda machine as their historical records and played along -- including the valuable pronouncement (among other omens) of a prophecy of his rise from the "mysterious east".
Mason speculates that it would have been an obvious survival strategy for Josephus, while held prisoner and before Vespasian became emperor, to have appealed to Vespasian as the one with real authority, the "real Caesar", along with his son.
It would have been win-win: Josephus can be honoured as a true prophet and noble priest of a great people; Vespasian as the destined (by the gods of all nations) heir to the power of Rome.
Many old prophecies hailed conquerors of Jerusalem
That such a prophecy was found to have "existed from of old" and applied to Vespasian is nothing unusual. Such discoveries and acclamations in such circumstances are in fact not unusual:
In real life, however, commanders of invading armies have always received exuberant affirmation from fast-thinking natives, their welcome often being full of providential overtones. “It’s not just our city council that considers you marvellous, Your Excellency; you are the One for whom our people have been waiting!”
Local elites who make such claims are expressing overt loyalty, but more importantly they are asking that their community be spared and protected by the conqueror. In Chapter 6 we shall see a diverse range of poleis rushing to welcome Vespasian and his army before he reaches Galilee, for just such reasons.
Rajak cites the example of Ibn-Khaldun and the Mongolian Tamerlaine,220 and we may add others.
Napoleon was regarded by Europe’s long-suffering Jews as a Davidic-Messianic liberator (Cheleq Tov), who made real again the biblical Song of the Sea (Exod. 15:1-15).221 He encouraged this.
A century later (October 29, 1898), Kaiser Wilhelm II was exuberantly welcomed in Ottoman Jerusalem, by its Jewish community among others. The first of three arches along his “triumphal procession” was the Jewish one, decked out in silk and carpets with gold letters, even though he came as a self-conscious Crusader who was claiming the city for Christian Germany. An enormous eagle mounted over the Jaffa Gate greeted him as he entered to plant churches and other signs of German culture. Still the legend on the Jewish arch declared in Hebrew and German, “Blessed is he who comes in the name of the Lord! We welcome you from the house of the Lord” — the line from Psalm 118 cited in Jesus’ triumphal entry222 — as Jewish school-children sang these words (Fig. 9). The Kaiser also received a parchment scroll inside a Torah case that read in part: “Be sure, O Kaiser, radiant with Heaven’s noble consecration, that the sons of Judaea also approach you rendering homage, greeting you reverently from their innermost bosom.” An accompanying prayer affirmed God’s choice of the Hohenzollems to rule in righteousness.223
And even an old Arab prophecy of the conquest by General Allenby
Not even two decades later (December 11, 1917), however, the British General Edmund Allenby would be similarly welcomed at Jaffa Gate by Jews, Muslims, and Christians - as the city’s redeemer from Ottoman-German rule. His surname invited the transliteration Allah an-nabi (prophet of God) among the Arab population, which British propaganda delighted in exploiting.224 There was supposedly an old Arab prophecy, recalling the one that Josephus made famous, that a prophet from the West would enter Jerusalem’s Golden Gate when Nile water reached Palestine (cf. Allenby’s pipeline from Egypt). The British government toyed with having Allenby enter via the long-sealed Golden Gate, but drew back from practical complications and the wish to avoid kaiserlich pomp.225
Context, context, context . . . .
Prophecies were part of the tragic landscape. There is always a prophet foretelling what is to be an outcome -- doom for some, victory for another -- in ancient narratives of tragedy.
It would not be amiss to exercise caution before building an entire case and historical reconstruction upon one such omen whether found in Tacitus or Suetonius or in Josephus.
The above in the main based upon the argument of Steve Mason,
A History of the Jewish War A.D. 66-74, 2016. pp. 111-130.