Richard Carrier offers some in depth detail in how Christianity began.
Richard Carrier Deconstructs Christianity in One Hour
I've watched at least a dozen of Carrier's debates where other Historians and Theologians have tried to argue for the existence of a historical Jesus. In every single case Carrier has torn their arguments to shreds. The more I hear Carrier speak - the more I'm leaning towards the position that the story of Jesus was told so many times people started to believe he was an actual person - but he may well never have existed to begin with.