Would it not be suspicious if I suddenly deposit a shitton of crypto into a new account in a new casino?
Absolutely to most, if not all casinos. You'll be asked to complete KYC right before your first withdraw or in more extreme cases, the moment the casino detects it.
Nah, I don't think so.
Casinos don't care how much you deposit (as long at the money is not flagged like stolen btc or whatever).
They will ask KYC once you try to withdraw a considerable amount of profits though, that's almost always like that.
As long as you are down they obviously never care since you are a profitable player for them.