Separation of powers was designed to prevent a few bad actors from seizing control of the whole system, as frequently happened in ancient republics. It's actual

Separation of powers was designed to prevent a few bad actors from seizing control of the whole system, as frequently happened in ancient republics. It's actually worked well for that purpose. It wasn't intended to defend against incentives affecting everyone who gets into any kind of office. No one foresaw that weakness. People keep talking about separation of powers because it was once a good solution to a problem that no longer exists.