Who knows, maybe online casinos even hire hackers to hack their competitors, because in this business, if a gambler leaves one casino, he will definitely come to another casino.
And I don't see any reason why casinos couldn't restore their status again, because they can continue to provide services to gamblers and from this, at the expense of the commission, they can restore their balances again, or take a loan from the state in advance and give gamblers their deposits. After which they can resume operations and gradually pay off the debt, because no one has canceled the commission.
It’s a weak reason to that since hacking is a crime which means their reputation might be dragged too once the hacker caught or blackmail them for being the master mind on the hack to other casino.
They will just focus on marketing to beat their competitors rather than resort to hacking that there’s no guarantee that they will successfully penetrate other casino security.
Besides, they just need to focus on their own business if they want to become successful since there’s a lot of competitors that is almost impossible to hack them all at one go.