Those hackers are very skilled and only needs a slim opportunity to penetrate what so ever they want to hack, I know they also hacked Stake casino some months ago and stole some huge amount of money too.
The hackers are very skilled but how were they not able to know that their plan can become unsuccessful if they will send the money to an exchange. Probably they did it intentionally or probably not, but that make it looks unprofessional.
Well, we can not tell if they did it intentionally or not but sometimes they don't use their details to create accounts on those exchange and even if the exchange discide to carry out an investigation on the account, they might be holding someone else rather than the scammers and they probably must have also move out the money from that exchange before they could even be discovered.