It's stolen property. They're never going to be able to keep it even if they do do some prison time. If their claim is that it's truly lost and they no longer have access, and then the funds ever move again on the blockchain, boom, right back to jail under contempt and other charges.
You can also do the time and leave the US after.
It's worth a billion dollars today. But in 5 years, who knows? Could be worth $10B. Could be worth $0.
Ooo so brave, saying Bitcoin will go to 0! No one has heard that before!
Is there a particular reason for the snark? We are talking about essentially a 5-year blind trust in a historically volatile asset.