(Matthew 10:23)When you are persecuted in one place, flee to another. Truly I tell you, you will not finish going through the towns of Israel before the Son of Man
If "Mark" (author) was a failed apocalyptic prophet, then it is expected that Matthew would have corrected his false prophecy, since Matthew would have recognized that the his similar prophecy wasn't realized by his time, being Matthew after Mark.
But it seems that Matthew was a false prophet, also.
Three alternative hypotheses:
1) Jesus existed and he was the author of the Logion.
2) Mark and Matthew where both failed apocalypticists.
3) Mark and Matthew were using a particular tropos: the image of the apocalyptic prophet for Jesus. There was no embarrassment in the fact that the apocalyptic prophecy wasn't realized when they wrote the Gospels under their same eyes.
I see that Carrier follows the hypothesis 2.
There is some scholar who argues for the hypothesis 3? Thomas L. Brodie?