The earliest date given for the authorship of Mark is 50 AD, and the date given for the authorship of the Pauline epistles is 51 AD.
I have to say that I have never seen a date for Mark so early. The date for Paul is what is commonly accepted. Even if Mark was 50 AD, that hardly gives time for Paul to hear of, gain access to, read, and finally reject the majority of Mark in favour of his own invented Jesus theology, then nip around the middle east establishing churches, so that he can write to them in 51 AD.
The dating of these books, frankly, is a mess, given how they were later edited and altered. There's literally nothing that can give us any confidence that the books of the Bible are accurately reporting any real history; they corrupt everything they touch. Anything with a connection to the Bible must be disregarded absent some kind of real evidence.
Am I the only one that detects a hint of fanaticism here? Even though I am now an atheist, I retain an interest in the historical and archaeological aspects of Judaism and Christianity. I can certainly entertain the idea of Jesus being entirely invented, and it would be interesting to see how that would fit around the historical charatcters of Peter, Paul, James, etc, and their rifts. But I think it is more likely that there was a historical Jesus, and the mythical elements of the story grew, as they say, in the telling.