Even if it's more logical for hackers to target a casino to steal its money than its customers' data, that doesn't mean that the casino is unaware of a possible doxs attack or their security is looser than the one they have for money. This is what I want to think and believe, at least for the top-tier casinos. People's data is precious and must be treated accordingly and ofc can't be replaced like money.
Even in another point that's also right because even if they just make strong security for only financial department and they neglected to the users kyc or the personal data, in my personal opinion I think that casino will also have the some hole for the hacker to loot their money also.
And also as well if a casino were able to just protect their money from the hacking attempt and just let it be go the kyc data stealing then I don't think there will be any positive reputation alive for that casino and in the long-term gradually they will loose the customer and maybe ended up they would gonna shutdown their business?