The most effective protection is a combination of discretion, strong security practices, and advanced wallet configurations like multisig and passphrase protection.
You could store passphrases in a hardware wallet in a bank vault in a small European country.
Physical security for digital credentials is the main point here, that doesn't always imply a regular bank, many modern banks lack the bank vaults of yore in any case.
Yes, ironic. But, of course, nothing in this attack has anything to do with blockchain or crypto per se. They could have been torturing someone for the password with access to the bank's old school accounts or safe deposit box.
You could store passphrases in a hardware wallet in a bank vault in a small European country.