I am a former a corporate standards and procedures writer for a major fortune 500 finance/insurance company. All corporate bodies, departments has internal and external checks and balances with regards to money from the lowest levels to the highest. In short when the Wells Fargo CEO says he did not know the fraud was going on for 5 years he's lying, did not care then or know and has no native curiosity of the possible future beyond saving his ass.

This was not a small group of thieves, but a global wide operation this approved at the highest levels by risk operatives, legal, accounting, card services, operations, information, security, recovery.