See the prisoner's dilemma. If both people are bad, they will have the worst outcome. If either of them thinks the other is bad, then they will also be bad in order to protect themselves. So the best outcome (you are bad, and they are good) is impossible, because they know you're bad and will be bad themselves.
So two bad people have a good reason to write a law preventing them both from being bad, because that's the best outcome they can get for themselves.
The whole point of checks and balances is to get good results from imperfect people. You can use the ambitions of one individual or group to hold the ambitions of another group in check.
I feel like you're just trying to be snarky and or gratuitously negative though.
Americans have deified their Founding Fathers to such an absurd extent that they seem to be unable to think critically. That maybe Hamilton and Madison were engaging in wishful thinking. That maybe the anti-federalists were right. That maybe Henry Clay's American System and his antecedent in Hamilton largely botched the ideal separation-of-powers republic from the beginning.
Granted, it uses an imperfect system of consensus to "do" this right now.
Oh wait....