Stood up? How? Steam couldn't even do that and they were far bigger than itch.io ever was. That's a bit laughable. Unlike Steam though, itch.io had no internal control of what gets it and what not and also offered if I recall correctly mostly payment through US services (and every delay that would come with that), so they literally have to go nuclear to be able to comply like Steam, which will inevitably hurt them financially, especially since it's way smaller team than Steam ever was. It sucks but there is not much they can do until they make sure they comply, which means a lot of games will be gone for some time and some will never come back.
How? Any way you possibly can. You or I don't know for a fact Stream couldn't have done anything as we don't work there and do not have access to their financials. If I were Steam I would go full elon musk and tell them to go f themselves (just like he did to the advertisers), then begin building my own payment processing infrastructure. Either that or by making my own crypto currency that doesn't rely on any other company.
Wild take in response to "The owner of twitter deliberately made its bot praise hitler and spout racist conspiracy theories, which is someone everyone fucking saw and only someone engaging in bad faith would deny that" but okay.
Also pretty wild that you're derailing the conversation like this. You on mastercard's payroll or something?