There is something wrong about this story because such amount of wallet can't be a hot wallet, I have never heard of that exchange and that means they don't have much liquidity that much and that kind of Bitcoin should only be kept in a cold wallet, storing this amount of Bitcoin in a hot wallet means they don't care much about security of their custody if such amount of Bitcoin can be stolen over night, it doesn't make any iota of sense but proper investigation should help.
I also don't understand what comes next to the mind of scammers. Who steal such amount of Bitcoin when you can't spend it, the transaction will never step a foot on any exchange because it will be reported and even some exchanges should be aware of it by now since it has gotten to a media platform like Coindesk. The hacker would just be moving coins and wouldn't be able to spend, this is what physics means when you do zero work, noting is achieved here.
Assuming the hacker cannot launder the coins and get to spend them, one option they may have is to talk with the owners of the hacked exchange and return most of the money stolen, with the condition they can keep a small percentage and that the exchange will not pursue the matter anymore on a court of justice.
This way the hacker gets to keep millions of dollars for themselves for no repercussion, while the exchange despite losing a great deal of reputation over the incident can reduce their losses, so it would not surprise me if such an agreement was possible between the two parties.