SEO contributes for sure, but I would reverse the statement here - it's more about new content and less about SEO. There's a feedback loop race to the bottom dynamic regardless
So you believe SESTA/FOSTA led to an unintended increase in the actual violence you'd see if you watched random videos on Pornhub?
I don't think much of SESTA/FOSTA, but I do think that's kind of a stretch.