There's another tradition called Romantic Satanism which was a 19th-century literary movement. It's basically what happens when a bunch of post-Enlightenment writers go "Hey, what if Satan was actually the good guy?"

Around this time was a lot of rebellion against both monarchy and the church, and they felt some kinship with the rebel of the story, not the despotic deity he was opposing. (God's actions in the Old Testament would be considered horrifying if they were carried out by a human.)

Modern Satanism's myth of Satan is a kind of reinterpretation or re-imagining, like a feminist retelling of a princess fairy tale.