Unfortunately it is very difficult to prove much about the earliest roots of the cult. But here is what I suspect:
The symbolism preceded the name. The name is a product of numerology. This is the reason that the
nomina sacra are letters written like numbers, with a line over them.
I also concur that it is likely the case that worshipers of Jesus drew from multiple cultic currents from the outset. This would be much like the origins of Kwanzaa or something.
I strongly believe that in its earliest phase the cult was seen as non-Jewish. Its likely the cult incorporated elements of Judaism but put them into a non-Jewish context, like Gnosticism. This would make sense given the role of Judaism in Gnosticism and also given "Paul's" comments about opposing the "church of God" because of his zeal for traditional Judaism.
What orthodox Christians have long imagined is that the Jewish establishment was so strongly opposed to Jesus that "good Jews" like Paul would have viewed Jesus and any followers of his as "outlaws" who deserved the most violent and extreme opposition.
But it is highly unbelievable. Rather, when Paul talks about his opposition to the "church of God" and trying to "destroy it", it sounds a hell of a lot more like Paul is talking about a foreign cult, like a Roman cult, that is being imposed upon Judea, OR that he is talking about something like Gnosticism, which is declaring a higher God that is going to overthrow the God of Moses.
Philippians 3:
2 Beware of the dogs, beware of the evil workers, beware of those who mutilate the flesh! 3 For it is we who are the circumcision, who worship in the Spirit of God and boast in Christ Jesus and have no confidence in the flesh— 4 even though I, too, have reason for confidence in the flesh.
If anyone else has reason to be confident in the flesh, I have more: 5 circumcised on the eighth day, a member of the people of Israel, of the tribe of Benjamin, a Hebrew born of Hebrews; as to the law, a Pharisee; 6 as to zeal, a persecutor of the church; as to righteousness under the law, blameless.
7 Yet whatever gains I had, these I have come to regard as loss because of Christ. 8 More than that, I regard everything as loss because of the surpassing value of knowing Christ Jesus my Lord. For his sake I have suffered the loss of all things, and I regard them as rubbish, in order that I may gain Christ 9 and be found in him, not having a righteousness of my own that comes from the law but one that comes through faith in Christ, the righteousness from God based on faith.
The fact that Paul lists his persecution of "the church" as proof of his standing as a Jew indicates that this is something that would have been seen by all Jews as something easily recognizable as a sign that he was a "good Jew".
This "church" or assembly, has to have been something so well known that many Jews were opposed to it. This sounds to me a lot like a Roman religious movement or cult, which would have been opposed by Jewish zealots opposed to the occupation. And certainly, such a cult could have been Gnostic in nature, claiming that a higher God was going to overthrow the God of the Jews.
Even if one assumes that there was some real Jewish Jesus who was executed under Pilate and that this figure was some sort of popular leader, such a Jewish Jesus, according to orthodox sources, was at best some kind of Jewish reformer, of which there had been many. There is no indications that this reformer was so well known that sometime in the 30s or 40s CE a "church" had already been well established following his death and that this "church" was so infamous that typical Jews would have recognized working to "destroy" this movement as a mark of being a Jew in good standing.
No, being a "zealous Jew" meant being opposed to the Roman occupation. Thus, whatever Paul was talking about had something to do with the Roman occupation. Certainly, being opposed to a movement that was aligned with Rome would have been seen as being a sign of a Jew in good standing, and/or being opposed to a cult which claimed that a higher God was going to underthrow the God of the Jews.
As for debate about whether Jesus was foretold by the Jewish prophets, this could well have been a long standing point of contention, given the nature of the Jewish scriptures, which are themselves highly critical of Jewish leadership.
