We don't know much about the early decades of Christianity because Acts isn't so trustworthy. What we have mainly are Paul's epistles to the Christian groups he was evidently founding or inspiring. And alas, Paul strangely ignores the historical Jesus. His churches look much more like quasi-Gnostic Mystery cults. If the Mystery cults could have been founded throughout the Mediterranean to worship fictional divine savior gods, why couldn't Christianity be just a Judaized version of that movement? That's the question mythicists like Richard Carrier, Earl Doherty, and even Freke and Gandy raise.

I don't mean to say, though, that mythicism is obviously correct. Remember, my view is that the matter is ambiguous from where we stand, two millennia after the events supposedly took place. I'm saying we can explain the data pretty well, with some problems for either side, in either historicist or mythicist terms. So we don't really know which theory is true.

For example, you suggest it's just easier to posit an historical Jesus to account for the founding of the early churches. But then why do those earliest known churches ignore the historical Jesus, under Paul? Shouldn't Jesus have been divinized only later on rather than right away? That's a big problem for historicists, so it's not so simple to explain the data by positing a historical founder.

You also strawman the mythicist alternative, which isn't that Christianity began as a lie. Did the initiates of the Greco-Roman Mystery Religions think they were lying to themselves by participating? No, they believed in the higher reality of their savior deity.

And there were levels of initiation. The lowest levels weren't entrusted with the cult's greatest secrets. So you'd have myths and symbols, but only the inner circle knew what they truly meant. Paul might have been teaching the inner, theological mysteries, whereas the author of Mark might have focused on presenting the outer, exoteric, allegorical narrative. As Christianity developed, the generations forgot that the narrative was supposed to be allegorical, as the churches got carried away with competition and political power, and the esoteric Gnostics ended up being persecuted as heretics.