Beyond the earliest days of the religion, early Christians were believers because they'd been converted, not because they were witnesses to supernatural events, just like today. The 9/11 hijackers believed in Paradise for martyrs, but that doesn't mean that that's true. We have no good reason to imagine that eyewitnesses wrote the gospels rather than someone simply documenting the Jesus story as it had developed within their church community.
Robert B. Seidensticker