If second-temple era Jews are “pagan” then the term “pagan” has been expanded such as to denude it of all meaning, even if we assume this evolutionary view of Jewish religion, which is actually a very questionable view.

There are plenty of unique Christian traditions too that didn’t come from surrounding culture. The veneration of relics and body parts of saints in particular was considered grossly alien and offensive to the pagans of the time. It was deeply countercultural to have such veneration for pieces of a dead body and to go so far as to build your places of worship around them, to kiss them, etc. And as far as we know the Christians didn’t get this idea from contact with anyone else, they came up with it themselves. It’s deeply myopic to treat ancient people as devoid of creativity or agency.