Couldn't an alternate explanation for the numerous copies and translations just mean that it was really popular at the time? Two thousand years from now we might expect to find more translations and copies of Harry Potter than any significant history journals.

As for why these types of conversations frequently end up with people talking past each other, there are too many vested interests in too many different sides of the debate for people to know in advance which points and interpretations they should be emphasizing. Are we discussing history? Religion as a concept? Religion as an identity? Epistemology?

As for myself, I used to be devoutly religious, I read the KJV OT cover to cover once and NT multiple times, plus the other books of my former faith multiple times, plus a number of apologetic essays. I was also learning about science and empiricism, and eventually found that my faith was full of contradictions and grasping at ever more tenuous archeological straws, while science provided modern evidence for its claims that could be verified and even rediscovered by anyone with the time and equipment.

So in these kinds of discussions, if you happen to be talking to a person with a background like mine, if you want to go beyond just factual discussions of historical discoveries and into the loaded territory of religious historicity, you must first convince such a person that fragments of ancient manuscripts should bear any modern relevance whatsoever in the face of what they would see as the significantly more reliable epistemological foundations of modern empiricism.