OF is significantly different from other social media in that the adult market has a lot of really weird market factors that make even new market participants able to access significant revenue. Most OF people aren't making 10 million, but it's better to compare OF to patreon where most small users are still pulling in a few hundred dollars a month at least - and that's a pretty significant amount if you've graduated from school into a pandemic market.
I also wonder if OF customers prefer paying girls who have less fans. This allows the person paying to have more personal interaction and to have more influence/control over the girl for less money. So market forces therefore would drive a long tail