Satanism isn’t a religion, if by religion one means a belief in God. It’s a fake belief system based on lies and evil.
I think it's sometimes a mistake to dismiss godless belief systems as being non-religious.
The idea that religion requires a god entity lets leftists get away with imposing their dogma on everyone else by simply refraining from saying "God tells us that...", or "God says..."
A more broad definition of religion would would allow first amendment challenges to leftist's ideological control of public education.