Christianity/Catholicism and Pagan traditions basically absorbed each other, even within Christendom power struggles concessions were made to accommodate and consolidate power. Can see this today more obviously in South America where Catholicism and animist indigenous beliefs have blended together, Peloponneseia as well.
As others have said, pretty much co-opted from existing traditions https://historyofenglishpodcast.com/2013/05/05/episode-24-germanic-mythology/
Christianity/Catholicism and Pagan traditions basically absorbed each other, even within Christendom power struggles concessions were made to accommodate and consolidate power. Can see this today more obviously in South America where Catholicism and animist indigenous beliefs have blended together, Peloponneseia as well.