It's probably the gambling expenses, if it's a constant funding in the gambling fund, the bank will definitely suspend your account until you've done some explanation that it's you who's doing all this stuff and that your bank account isn't compromised. Or you're not telling us everything about the bank transactions OP, that there's some suspicious activity going on that got your account flagged and banned, that's the other way that can get someone's bank account banned.
It seems like it. If someone managed to steal a credit card and had sometime before the victim realizes, they would try to buy valuable stuff as soon as possible for them to sell later, though, criminals have realized that doing so would make easier for law enforcement to find them and charge then with financial crimes, so what they do is try to use the stolen card to buy cryptocurrency on an exchange or in a casino, as much as they can so they can try to withdraw it to a wallet under the sole power/influence.
I would also like to add that using a card on gambling sites and betting could block them, depends on the terms of services of the bank itself. There are some banks which frown upon gambling in general, because the economical repercutions it can have on their clients, so they cancel and block when they detect their users are partaking in gambling.
I have read about the concept of Halal banking before, basically banks which are owned by Muslins and do not like to get their finances involved with warfare, gambling, pork production, etc. but I am not sure their common policies are to block those card used personally by their clients to gamble/bet.