I think Lemmy has a problem with history in general, since most people on here have degrees/training in STEM. I see a lot of inaccurate “pop history” shared on here, and a lack of understanding of historiography/how historians analyze primary sources.
The rejection of Jesus’s historicity seems to be accepting C S Lewis’s argument - that if he existed, he was a “lunatic, liar, or lord,” instead of realizing that there was nothing unusual about a messianic Jewish troublemaker in Judea during the early Roman Empire.
It’s not quite certain that Jesus and Paul actually met in person. So all his writing might be apocryphal. His word might have become christian canon, but he is not really a source one can trust.
While Jesus and Paul likely never met in person, the point is that Paul is writing to established Christian communities within a few decades of Jesus’s death. There are already churches with established leadership and community structures.