Why would the apostles all die martyrs deaths for someone who didn't live up to his promises? Especially since the gospels show they weren't of the most courageous character either. That is pretty convincing to me, I don't know of a good counter.

Also, if there were so many Christian communities so soon after Jesus' death, then there would be a good community of knowledge to filter false and true accounts of Jesus life.

Finally, why didn't any of the other unorthodox accounts start similar communities? Why are the communities so similar in their beliefs about Jesus, if it is quite likely to have been made up, as you suggest?