There's a huge difference between the idea that the Biblical character of Jesus was based on a man who really did exist, and the idea that the Biblical character of Jesus really did exist. A man named Jesus could have preached religious messages and gathered a following and become controversial and been executed for treason due to false accusations from bitter religious leaders. The additional claim that this man was also god made flesh, and that the whole thing was his plan from the start, requires far more than testimonials.
Jesus is, after all, not the only person whom others claimed was divine. It's not a rare find; many ancient men claimed divinity and/or were granted such by others. Heck, it happens today.