https://www.justice.gov/usao-edny/p...leads-guilty-international-scheme-defraud-nft That sounds like justice was served, but How can he get to keep the ~$1.6 million difference?
My guess is that's not what happened. What probably happened: He amassed $3 million and it was held in crypto. By the time the authorities seized it and converted it to fiat money, it was only worth $1.4 million.
They can still say he owes the remaining 1.6 million. Just because you don't have it doesn't mean you don't owe it. He got a good deal.