Then he appeared to more than five hundred brothers at one time, most of whom are still alive (1 Corinthains 15:6)
A popular theory about Christianity is that the whole thing is rather a mistake! Yes, Jesus was a great teacher but he was no messiah, let alone God. People in the first century were a superstitious lot, and would believe in any old nonsense. Over time Jesus became a legendary figure, a sort of spiritual Robin Hood. The gospels were written down much later, and by that time the legends had become hopelessly tangled up with the real Jesus.
A few things need to be said here. First of all, the scholarly consensus was that Matthew, Mark and Luke were all written by the late AD60s with John perhaps a couple of decades after. Paul’s letter to the Galatians is widely dated to the early 50s, or even late 40s. Behind the gospels are decades of oral tradition, as you would expect in a culture where literacy rates were low, so they did not spring out of nowhere when they were written.
Secondly, do note that in the gospels many eyewitnesses are named. It would seem that these are people who were still part of the community of the earliest church, and could be asked about what they saw. As named witnesses, they can vouch for what was written and this approach was well known in ancient literature. Moreover, the names of people and places mentioned in the gospels reveal a close knowledge of the area at the time of Christ (which would not be the case of a much later author).
Thirdly, the ancient world was not as credulous as we would like to believe. In particular the Jews, with their strict adherence to monotheism, were not likely to come up with the idea of that God taking human flesh. Read through the gospels, and you will find plenty of people skeptical to Jesus’s claims!
The truth is that we have very early written evidence for the claims of Christianity, evidence backed up by the names of eyewitnesses. The claim that this is all a later legend simply does not hold water.