I understand the centrality of the god-figure's death and resurrection, following the Osiris tradition cemented millennia before the time of the hebraic patriarchy. But it is one thing to be killed and resurrected, and wholly another to be recorded gadding around preaching doctrine, first. I don't think there is anything in Paul about that.

That Paul does not encompass the whole of later writing is far from surprising. Making a new religion is hard and thirsty work, and you don't know what will be needed until you have got congregations and sees together, and seen what would need shoring up.

I have also seen how the whole "redeeming original sin" rationale for the resurrection stunt was invented maybe centuries later, and that various sects had numerous other theories about it, until it was recognized that the question was causing too much dissension, and one theory had to be picked to rally around.

I get that people can be upset at discussion of possible ahistoricity of a Jesus figure. I can't see how anybody who has faith could be upset about it, though; to be upset about it, it seems to me you would have to have doubts yourself, and fear that discussion might turn up more facts that would cause you even more doubt.

In any case, citations of documentary evidence all of which was in the possession of the Church for millennia, and which it generally would have had to take initiative to transcribe before its paper rotted and crumbled, cannot establish any objective authority. The Church is the prototypical Interested Party. Certainly we have copious examples of forgery both early and late, so we need more than ordinary attestation to establish facts.