Probably because the interlinking of deposits and debts across these institutions would lead to a near if not total collapse of the financial system. Quite a nu

Probably because the interlinking of deposits and debts across these institutions would lead to a near if not total collapse of the financial system. Quite a number of large banks DID fail in 2008-9 at first, before congress stepped in. Dodd-Frank was supposed to prevent this from happening again, but a disturbing number of relatively trustworthy advocates have suggested it is too weak to do so.