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 be forfeited or become unsuccessful if they will send the money to an exchange. Probably they did it intentionally but that make it looks unprofessional.
Running a casino is a very lucrative business, though it's very tough in the very beginning when the casino is still struggling to gain loyal players.
The beginning is not tough at all. If you have money, you can have a gambling site. All that is needed is that you will need to spend enough money especially on marketing.
Also if it is a crypto gambling site, it is better you have extra coins in case if hack. Just as Stake and Metawin did. Leave more coins on cold wallets.