They were not persecuted to any real extent and the few that were was because they weren’t giving sacrifices to the gods. Not because of any moral reason.

You can even see it in the first time a political leader mentions them. He says that he lets them go if they just agree to make an offering. The Romans had zero problems with charity the Romans had zero problems with people being nice. They had a problem with not respecting the gods because they “knew” that if you didn’t bad stuff would happen.

There was no golden age to Christianity that they fell from.