>They 100% do.

Not even close. For the most part, they're bound by EU regulations.

>It isn't a legal thing to do because they didn't give a reason why. ANd if they do give a reason it must be legal to the local legal framework. Is being in the weapons industry a legal argument by Czech laws to close someone's account?

Banks are only obligated to give a reason for closing basic PAD accounts. No such obligation exists for normal bank accounts.