Comment by tetha

Black Sabbath, of which Ozzy was the frontman, is considered to be either one of around three, or the one founder of heavy metal. It may not be entirely right to say so, because there was a development going on around that time, but the entire giant metal genre goes back to these few guys, with Ozzy being one of them, in this timeline.

This heavier and more aggressive music was paired with a more krass and evil image to distinguish it more. That's where a lot of the dark, evil and satanic themes come from. Both of these are why he is the lord / prince of darkness in our circles.