Itch DID back their content creators. If they get blacklisted by the payment providers, NO ONE gets paid. The problem is not Itch. The problem is that banks can legally choose to stop you from spending your money.
It's the payment processors here, not the banks, but yeah.
Payment processors should only be able to deny transactions if a) they have legitimate reason to suspect fraud, b) you don't have enough money, or c) the transaction literally cannot be completed because important information is missing.
Yes they did. You just have the fool idea that backing creators always means doing the stupid thing that results in absolutely no one getting paid. Punctuation.