This is a really interesting point, Velle! 
Although I’m far from being an expert in Slavic folklore, from what I’ve seen, may of the pagan gods (as well as local celebrations and traditions) in this part of Europe could not be erased by the arrival of Christianity, so instead, these local enigmas were adapted by the church.
It’s also interesting to note how similar beings, deities, and creatures of legend are across cultures around the world- the many faces of Cernunous/the Horned God/Veles or the Morrigan/Morana/Marzana, for example.
It’s always interesting to see how things that could bring groups of people together often cause disagreements instead. It makes me realize how important and valuable it is to study different cultures and represents of paganism/religion around the world! 
