And that is one of the biggest misconceptions of crypto stuff.
Law and contracts (1) determine who owns what, not who happens to currently hold it.
That's why the founder can threaten them with the IRS, because they (likely(1)) do not rightfully (as defined per law) own it.
This is also why NFTs are kinds stupid, because you totally can sell someone a NFT which "claims ownership rights" without selling them any ownership rights legally seen. Sure it's most likely fraud as you deceived people, but only if. So telling people you sell them the NFT but not the think behind the NFT would make that pretty legal. Like you can sell a certificate about the correctness/quality of a picture without selling (or even having) that picture.
(1): Smart contracts are not contracts, they are computer programs. They might also contain contracts, but that doesn't mean that just because something is done in a certain way in a smart contract it is legally binding, legal, or anything (Well, that's also true for contracts themself).