I am beginning to realize just how many historical arbitary happenings decide these things. For instance, when Luther came about, Danes 'became' protestants because the then king liked the idea of being head of church as well as the country. And now we are. Much the same in a lot of other places.
I am no expert on satanism, but I do know it is the Christians that create a devil who hates people. The little I now about satanism is that it is actually many things, that some of it was established as a protest against and attempt to liberation from the many restrains Christianity places on people, that some of it is sort of nature orientated, and that some is some sort of magical universe.Satanism? I don't know how mainstream it is, but it's been around for a long time.
Mainly I think it is a figment of Christian imagination, a way to demonise whatever they do not like.
The word 'satan' is apparently Hebrew for 'opponent' or 'accuser'.
Fear of satanism is an example of how deelpy imbedded christian ideas are in us, like it or not, like the idea of who Baal or Astarte was, or Loke.