Most pagans (99.9%) will tell you that Satan is a christian boogey-man, and that modern witches don't believe in him. So why would a goddess-loving (and horned god-loving) pagan migrate to the Satanists?
I think for me it boiled down to the pagans getting fluffy-bunny in recent years. Before there was a computer in every house, and only a few had the interwebs, there were pagan publications - Green Egg, new Moon Rising I both subscribed to, and bought some other ones at Borders (I love their periodical section). I saw what I had loved as an underdog being turned into, as Morning Glory Zell (from the Church of All Worlds, a sect developed from Heinlein's Stranger in a Strange Land) Jehova in drag (The Goddess).
Bad sentence structure, and I'm sorry. When I was learning the Craft, it was way more hardcore. As Z. Budabest said in her Holy books Of Women's Mysteries, "No Brownie Points are given for being a dumb-dumb. I can't help you if you won't read." (I paraphrase if I didn't get it right). I came from theOld School of reading your way through the UNABRIDGED Golden Bough, and actually read Crowley, even if you thought he was a mountain climbing blow-hard. My last days with pagan mags were decided when I read how many pagans were eschewing spell casting, and 'leaving everything up to the Goddess" or because of the popularity of movies like The Craft and TV shows like Charmed had teenage girls coming in droves.
Satanists were more like the futility of cat-herding that Anton LaVey wrote about, and I was feeling that shit. So I explored Satanism more than I did in the 70's (I read every occult book I could get my hands on) and hung with some groups online - not too much of a commitment there.
Until I met Grant, and turned him on to a particular flavor of theistic Satanism that portrayed Satan as our true maker and creator. some really dumb shit 9as i look at it now, but it was the bonds finally breaking). He went after it like a fish to water, because it pissed off his parents, and gave him license to do whatever he wanted to. I liked it because it gave me license to do what i wanted to, plus I dug the historical Satan,the Milton Satan, the Byronic Satan, the Satan as a concept, but try to explain that to a christian who hits you up in the grocery store when you just want to buy some beans!
I liked the Adversary. So I played with Satan for a few years, and have to confess to still liking the old fellow. I think my favorite cinematic Satan is Al Pachino as John Milton (har-de-har) in the Devil's Advocate.
His final polemic reduces down to what an absentee landlord god is, and says, "Worship that? Never!"
I had Isis tell me the same sort of thing in a dream. "You bend a knee to no one." She said.
It was a small jump from there to realizing that all the tomfoolery was basically nonsense, and besides the residual shame and upset that I spent so much money on books, crystals, incense, herbs, oils, soaps I made and other woo-stuff, and realizing worse of all that I was cold reading fools when I did their cards, and gave false hopes, bad information, selling a product that didn't work (Money Drawing oil is useless). Too many good decent people will reject junk like Noah's Ark, but will read their horoscope. Co-Workers still ask me for card readings, and I say I will give them, but it's entertainment. I had one say, "Well do you know someone who still believes in it?"
Sister, save your money.