4 million is certainly a big number for a casino, did they get the money back?
The hackers don't seem to be very smart because they sent the funds to a CEX so they could be traced quickly.
It happened only yesterday, I don't think it is too easy to recover the funds in just 24 hours. Even if they report to the CEX and ask them to freeze those accounts, the CEX won't return the funds to Metawin without following the procedures. Probably Metawin has to file a case against the hackers send a copy to the CEX and follow some other process to get the funds back.
I agree that the hackers aren't very smart. They could have used mixers and then some instant exchangers to swap the funds and then sent them to CEX to cash. But they sent them directly to the exchanges which was already identified.