Collective Shout is just the front and their purpose is to take the heat for this.
There is no chance in hell an organization like that wields anything close to the power required to force these kind of decisions.
Either it is the payment processors or the regulators, or a combination of both, or some other kind of group behind the scenes. Personally I don't know what the true answer is, but it's clearly not some activist organization.
It's not power, it's volume. Groups like Collective Shout are "squeaky wheels". They send enough letters/phone calls/emails to a payment processor, often via the company's legal team, often citing the processor's own terms and conditions, until the company caves from essentially peer pressure and takes all the whining and pushes it back onto their customers (vendors like Steam and Itch).
It doesn't take a lot of people/very big organization or a lot of money to do, just a willingness to be loud and obnoxious, but in a legal way.
It's the same thing with DMCA trolls that send takedown letters to demonetize things like YouTube channels. They don't need a lot of people/power/money, just a willingness to complain in volume and leave the evidence and fact finding to other people and/or automated systems like YouTube's auto-DMCA.
It is classic 1970s TERF stuff. Dworkin identified real problems, but her solutions are bad and make the actual problems worse by targeting already-targeted people for greater policing. What they do do is give suburbanite women the rush of power and control, building their own little evangelical theocracies.
There is no chance in hell an organization like that wields anything close to the power required to force these kind of decisions.
Either it is the payment processors or the regulators, or a combination of both, or some other kind of group behind the scenes. Personally I don't know what the true answer is, but it's clearly not some activist organization.