
Anthropology tells us that looking at religious sites will have layers and layers of past religion that got built over it. The moral center of a society is its religious bodies. That is why religious structures are typically better built than the homes and other buildings around it. What that means is overtime it’s from the shamans to now pastors or priests.
There are native Americans who believe in and practice Christianity, and the Greeks starting converting to Christianity after the apostles spread the gospel to many nations including Greece. The Greeks even had a likeness of what they called “the nameless God.” The Greeks themselves identified it as Abraham’s God after meeting with the apostle paul. Christianity spreads because the Hellenists, Nordic pagans, and other cultures began confessing Christ en masse in the years after Christ.