because the payment providers have 99% of market share?

And why is this the case when a variety of cryptocurrencies are trivially available to the public.

Maybe because they had 30 years in establishing complete domination of global online economy and all traffic even the one that ends up in crypto goes through them ... Also there is nothing trivial for the public.

and 99% of their revenue was from porn so i guess this business-ending decision is close to cryptopayment-parity

I imagine their options were:

* switch to crypto entirely

* keep credit cards, but block sexually explicit content

I doubt there was middleground where they could accept crypto for sexually explicit content, but still accept credit cards for everything else.

Which makes me think that a smart move here would be to spin off a second company that does allow this content, but only accepts payments in crypto. I suppose if they don't, there is a opportunity ripe for a competitor to take advantage of.