Earlier quoted context omitted.
He is the CEO. He should have known 5000 employees were engaging in fraudulent operations.
Wells Fargo has 265.000 employees. A CEO certainly has to make sure that there's internal oversight according to regulations and industry standards but it's not his job to personally go spying on people (try doing that on 265.000 employees) or implement the Wells Fargo Gestapo. If it cannot be proven that he knew about it or encouraged this behaviour then he cannot be held legally accountable. It's like demanding the…
But in general a CEO should have a duty to ask questions why a certain division seems to be doing well. Maybe it has to do with earnings targets that are simply unachievable? I see that in my own company. The top guys are setting shorter and shorter deadlines and in my view the quality of engineering suffers. Top management doesn't technically know when people are cutting corners but they could easily have listened to people that the demands are too high.