To protect an insured bank that is part of a larger organization, a supervisor needs to have the authority and tools to understand the risks that exist within the parent organization and its affiliates and, if necessary, address any significant capital, managerial, or other deficiencies before they pose a danger to the bank.
This is particularly true today, as holding companies increasingly manage their operations - and the risks that arise from these operations - in a centralized manner that cuts across legal entities.