If the courts don't know about the crypto that's another thing, but that's just the same as moving your money into an offshore account and not telling anyone. It's physically possible, but isn't legal as a way to get out of paying what you owe.
I'm a little surprised (or not) at the naivete of the cryptocurrency community "It's digital" "It's anonymous" "It can't be seized or controlled by the government". Sure, as though these extremely experienced professionals and very powerful institutions are going to read a tweet from one of the crypto maxis and just throw their hands up and say "It's on the internet, I guess there's nothing we can do about it".
These groups are very, very good at what they do. They've seen it all and even if it's XMR (or whatever) with the proper motivation they will find it (and you). Very, very few people and organizations have the full skill set required to evade these authorities.
I read the indictment. They were arrested and charged. We'll see how the defense plays out but from a read of the indictment they made plenty of mistakes and will (likely) end up going to prison given the conviction/plea rate of federal prosecutors.
Once convicted a federal judge can order them to give up the monero (as I said in my original comment). On top of their time in sentencing for the original crime they can be held indefinitely until they comply with the court order.
In the end they'll go to prison and the government will squeeze them for whatever they can get.
[0] https://www.nytimes.com/2022/02/13/technology/divorce-bitcoi...