Also, Paul’s writings obviously antedated his death (duh), and the earliest of them was probably in the late 40s or early 50s A.D.
Many of the apostles would have thought that the Second Coming would be within their lifetimes, and that the most important thing for them was to get out and PREACH to as many people as possible. . .since as has been mentioned, public literacy rates were low, and most people relied on word-of-mouth teaching, the sort of teaching Jesus Himself did in his 3 year ministry. Of course, they would also write or have scribes dictate for them in their communications with people far away, and as time went on they also began to write down the gospels and other writings, as well as correlate what they knew AND what they had written regarding Jesus (we know that not everything Jesus did or said has been “written” down, that many things have been passed along via Sacred Tradition), IOW assimilating the O.T. works which Jesus had referenced.
And at the SAME time this was all happening, Christians were being ruthlessly persecuted. In that dangerous atmosphere it would be a lot easier to go to a place and have someone “talk” to you about Christianity, especially in an “oral culture”, than it would be to go somewhere and READ about it–any writing could be found and confiscated and serve as evidence against you, so it would be indeed quite DANGEROUS.