I think you're misinterpreting the scale of Wellsfargo. The CEO probably doesn't even know what onlyfans is, and they manage almost 2 trillion dollars.
The CEO knows their business model; it's to scratch out every last penny they can, however they can, just to fulfill some quarterly earnings report. Almost every public company is now a growth company, so it doesn't matter how much they already profit–what matters is that they profit more in the next 90 days. He/She doesn't need/care to know about onlyfans–they simply care about hitting their targets.
...so why would they want to leave money on the table by forcing Stripe to ditch a clearly profitable client company?
Reputational risk. Some journalist gets wind of an ad on Youtube that's playing for a neo-Nazi video, it gets written up as "$COMPANY is supporting Nazis!" despite the fact that it's largely out of the control of $COMPANY, several companies collectively freak out and pull advertising money, and everyone goes hunting for where their pipelines might lead to similar pearl-clutching associations and PR disasters.
But that doesn't explain the documented unethical - if not illegal - conduct of Wells Fargo overall. Otherwise they'd be more like the Disney Co.
I think you are underestimating the scale of operation choke point.