That's not true, anti-sex work and anti-porn activists have specifically been pressuring payment processors to assume these policies. The processors as the critical control point of this whole thing was identified decades ago and conservative christian think tanks have been pursuing this path since then.

This is part of a long-term plan to de facto ban lgbtq content without having to deal with first amendment protections. First have the payment processors ban explicit content, then have queer content categorized as explicit.