When I was a teenager, I went to church, and almost every ‘Christian’ there was a complete asshole. What makes it worse is that they try to justify it. This honestly made me think that if God and Satan were real, I’d want to know Lucifer’s story. Maybe he’s not actually ‘evil.’
Good chance what we call the Satan at some point we’re originally a god from a pagan religion, like Beelzebub for example. If they were good that depends, if they were replaced in the first place perhaps that old religion was worst compared to what predates Christianity, another thing also is perhaps replaced because were forced to by the invaders.