How did the writings of the NT come to be?

[The Grand Nudger]

Because it would have been a huge expenditure of resources to contemporaneously document all the claims of all the religions in the Roman empire.

Good thing they had resources to spend then eh?

The adherents to those beliefs for the most part.

You think that the Romans allowed conquered peoples to write history? That's rich.

Then it will be easy for you to support your position by showing Roman documentation of current religious claims during the first century.

LOL, look at you trying to narrow the scope of my statement in your response in the hopes that nothing survives. Normally I'd call shenanigans...but in this case it doesn't matter....

You mean documentation like Annals, Histories, and Germania..just to invoke three examples from a single author? All three works make mention of various (current) religious practices and claims of "pagan europe" (information, I have to add, we cannot seem to source from these people themselves as they don't seem to have been so keen on writing this down as you imagined they would be). Religions and superstitions that the Romans were unlikely to have shared. Perhaps you would prefer to read what Plutarch had to say about Mithras? Pliny the Elder wrote a great deal on the "history" of the magical arts, including those bits considered "superstitio". That's the lazy google search version (with your demands of narrowing scope also accounted for). Enjoy. Turn the dial back or wrench it forward and we find even more. Romans were interested in this sort of shit, at least interested to write a ton of it down - except...apparently...in the case of Jesus......