As a counter example, should the US government not try to stop the cartels from using Swiss banks for money laundering because some arbitrary contract was already in effect?
In other words: Monero might be getting some friends on the Fed's crypto blacklist over this case.
Regarding "profiting", it is a good question, and that's what I don't understand in this case. To my understanding there is no direct fees in Tornado Cash. But there are Relays, which, to my understanding, allow to withdraw to a fresh address and take a small fee for that. Anyone can run a Relay, and the use is optional. I think those guys were running one of them too.
A Relay doesn't know who is who and cannot limit withdrawals of money deposited by a sanctioned entity. But as they were told that some of transactions are likely illicit, even though they don't know which particular, they knowingly profiting off it in general. That's very broad and later can be applied to anyone.
Similar can be applied to mining. In general ETH, miners do know the addresses and they do not accept transactions that include sanctioned addresses. So they are fine. But for Monero example, it's the same problem. Even though they don't know the transactions participants, they may make profits off illegal transactions.