Christianity is effectively a branch of Reform Judaism that really started only after the Romans destroyed the temple in Jerusalem. Then you have Rabbinic Judaism without a temple required, and Christian Judaism without a temple required (the fig tree having withered away). Only after the ews were unable to convince their kin did they eventually turn to the "gentiles" to convert them. Jesus was probably just part of the anti-imperialist resistance against the Roman empire, just like people are fighting against the US empire today. Crucifixion was the Guantanamo of Ancient Rome.
There are some interesting arguments about him not existing AT ALL, though, which are worth checking out, despite the mainstream of historians not sharing this view:
Edit:
Maybe you could say that Christianity died the moment when people started supporting it not because they believed it's true but because they believed it's politically useful. Which is basically the Jordan Peterson argument. Ironically enough, this disdain for objective truth in favor for "usefulness" makes them what they claim to despise so much: dreaded MODERNISTS. Charles Peguy once wrote that "a modernist is someone who doesn't believe what he believes." This is absolutely true for all these non-believers who support Christianity not because they believe in Moses, Jesus, Paul, etc., but because they think it's useful for their cuckservative agenda or whatever.