When a bank closes your account, the right to defend yourself looks a little different, because the bank is not allowed to tell you why by law. Anything concerning financial intelligence, such as if your account was closed because the bank’s compliance system threw an AML flag, is to be treated as secret information under threat of criminal prosecution.
Can confirm this to be the case. They ask the questions, you have to produce whatever documents they ask for, no matter how insane the ask.