But the exact extent to which that’s a good point is also the extent to which you’d want to print that very detail: because it gives people the ability to say, now, why would they put that in, if they were making it up? Therefore they weren’t making it up!
(Like, if I’m telling you the story of how I totally defeated the heavyweight champ in a straight fistfight, and I say “but I have to admit, he had me worried for a minute; he dodged my left hook, and slipped a couple of really deft punches past my defenses, before I spotted the flaw in his technique and knocked him out” — that doesn’t make my story true; it just lets me throw in a “hey, if I were making this up, why would I say that?”)
Such a detail (if true) could be evidence of fallible humans and thus an imperfect book that is someone more true because of it. Or it might just be a very inconsistent book from which little factual information can be gleaned or trusted.
None of these good points address the son of god problem. Since the Gospels were written long after the events, even if the disciples had died for the cause (and there is scant evidence of that) perhaps they died thinking Jesus was the true Messiah, who was not supposed to be the son of God, which is a pretty absurd concept in Jewish lore. (But not in pagan lore - the Gods spewed out sons all over the place.) So the argument in the OP doesn’t hold up, even if the premise had been true.
History is filled with cult followers who died for their beliefs. That doesn’t mean their beliefs were true, only that some people thought they were true. Don’t confuse beliefs with factual truth.
And, taking things at face value for a moment: why does Joseph come to believe the claim in question about Jesus? Per the text, he thought it was true because he heard it from an angel…
…in a dream. If we take that seriously, then people back then would believe stuff as if they’d heard it from an angel in real life while wide awake if they instead merely hear it in a dream while asleep.
That is, as far as I can tell, exactly how easy it was for them to start believing this stuff.
Judas isn’t normally accounted among the apostles, for obvious reasons, so James the son of Zebedee is the only one whose death is mentioned in the Bible. All the other deaths were only recorded by tradition, so are (literally?) apocryphal.
For a more educated and longer take on the subject, check out Zealot: The Life and Times of Jesus of Nazareth, by Reza Aslan, a noted scholar of the sociology of religion. His conclusion from the historical record is that Jesus was primarily a political revolutionary who also worked some quasi-religious themes into his preaching, but his primary goal was the liberation of Judea from tyrannical Roman rule. He was crucified mainly for being perceived as a threat to the Roman state. The alleged inscription on the cross, INRI, if true would have meant “Iesus Nazarenus, Rex Iudaeorum”, or “Jesus of Nazareth, King of the Jews”, sometimes described as a mocking humiliation but in reality was probably meant literally. The “Son of God” stuff and the rest of the mythology was created over the ensuing centuries, formalized in the fourth century by the Nicene Creed and its amendment, the Niceno-Constantinopolitan Creed, which established mainstream Christianity.
It sounds like you think this detail would be left out by someone who was trying to persuade us of something, because it’s an unpersuasive detail; and because it’s unpersuasive, the fact that they left it in is persuasive, making it a persuasive detail.
