The Christians of old had a habit of taking the old tradition and making it theirs. This made it easier to convince the natives that they were on the same page. Sometimes it is the other way around. The natives will acquiesce to the Christians, but secretly keep their old faith.
Look at the Celtic cross. It is a cross superimposed on a circle. The trouble is that the symbol was perfectly fine before the extra lines got added. Originally it was two equal armed lines inside a circle. Think of a plus sign, limited by a circle. The Christians came along and said “Hey, look, we agree!” And they added lines past the circle to make a crucifix.
Trouble is, the symbol means more without the extra lines. The symbol means that we are all connected. It symbolizes the intersection of the divine and the mundane. It symbolizes where spirit meets flesh.
The cross says the same thing, but the cross only appears when Christians have appeared and put it there. The circle cross, or equal armed crosses, appear all over the world and all mean the same thing.
They mean that the divine is with us. This is a holy place. This is a place where God is.
The fact that these different cultures have the same symbol meaning the same thing – that there is something larger than this perceived reality – is pretty amazing. It is even more amazing when you realize that these cultures had no contact with each other. To me this is proof that God exists.
Then there are the Druids. Christians took the oak groves they worshipped in and tore them down. They took the trees and turned them into pews. Instead of a faith that celebrates the Creator in the midst of creation, people were made to sit passively on the very trees that had sheltered them.
Rosary beads are another example. The pre-Christian people used beads for protection. They used amethyst as a ward against drunkenness. They used rock crystal for purity. They used red coral and garnet for similar purposes. Then the Christians came along and said that they are worshipping the stones themselves so they made that a sin. Then when they started using rosaries as a way to measure their prayers, guess what stones were used?
This is no more evident in the Haitian beliefs of Voodoo. They took their gods and folded them into the Catholic saints. They are still worshipping their gods. They just have different names now when the priest comes around.
The old faith gets transformed into the new faith. It gets recycled, reused, repurposed. The old never left, it just changed its face.