Steam or the creator shouldn’t be a central authority: If you have a game on steam and want to sell it to someone and they then activate in on epic, that should be possible. There should be zero influence from those parties over what happens with the NFT. It would also be legal, at least over here, to procure an erm backup copy from somewhere if you have such an NFT. And the NFT can live on after the original minter (presumably the publisher) went out of business. Say, GOG or archive.org could offer a service where the gamer pays a small fee and they can download binaries+emulation environment for those abandoned NFTs.

Neither the publisher nor the original store have any legal standing preventing any of this because exhaustion. Which is also why you can get Windows keys for dirt-cheap in e.g. Germany: There’s a small cottage industry buying up volume licenses at bankruptcy proceedings and then sell them on, unbundled. Microsoft can do exactly as much about it as Coca-Cola can stop you from selling individual cans from a sixpack.