Why did Christianity survive?
The myths of the virgin birth, the godman bringing salvation, and the resurrection are not unique to Christianity. They were common in the ancient Mediterranean. Here’s one source among many.
What was it about the Christian myth that made it durable?
Was it simply because they won wars and thus were able to write the histories as the victors? Was it the alliance with Rome when the emperor declared it the state religion giving the sect access to power and money? Or was it something else?