When leaders mess things up, why are companies slow to deal with them?

just don’t get it!
With more reports about ethics/compliance issues multi billion dollar fines being paid out shouldn’t these companies hold their leadership accountable for the decision that caused these issues?
What’s the problem here?
Aren’t leaders supposed to:
• Set the tone for the work environment to be one that is positive, inclusive and empowering.
• Model the behavior they want others to emulate.
• Be the change they want others to embrace.
• Live the values they preach, promote and expect others to do the same.
If they don’t do these, why keep them?
How many chances should a leader of any organization have when they have done something wrong i.e. illegal, etc? How many? When these leaders are kept on board, doesn’t anyone see what happens to the morale of the employees? Don’t they understand that customers, both present and future are watching what happens to resolve these situations? Is it the legal process that keeps them in power? If so, what does that say about the effectiveness and the value of compliance training? I wonder if senior execs participate in their organizations compliance training program ? Certainly one can be unethical and yet complaint right?
Aren’t all employees expected to play by the same rules? If mid level leaders were to have done serious harm to the company would there be the same hesitancy to deal with them, or would they be dealt with immediately? Shouldn’t the “no exception” rule apply to ALL employees? In addition, what does this tell employees about the importance of all their compliance and ethics training when on one is held accountable?

And where does ethics come into play in situations like these? How often is the term ethics used with a leader’s wrongdoing? Why not? Because how do you prosecute someone for being unethical?
I just don’t get it.