This is a big question that ordinary guys like us maybe hard to answer. I would guess that big banks can be so corrupt is because they are just working for money...the more money they can get the better it would be for them and their stakeholders. In other words, there is no involvement with the people or those they are servicing, in the firs place. As shown in the past, the government is very much willing to bail them out so they are now taking excessive risks because they are sure of support once something can really go wrong big time. Now, the mindset can be so different for credit unions. Here in my country, we don't have credit unions but we have credit cooperatives which have similarities in concept, design and implementation.