If it were so simple to revoke these keys as OP is implying, why would the game publishers be telling people to literally steal their games instead of buying on one of these key resellers?
What G2A is selling is usually Steam keys. They’re not always stolen through credit card fraud but also through pretending to be game media for review copies.
I haven't been involved in the project for a decade or so but I was one of the founders of OpenRA, so thanks for recommending it! I'm very happy it's still actively developed nearly two decades later.