Part of the problem is our Constitution. It is a wonderfully idealistic document. Unfortunately there are no hard rules that would allow the system a means for quickly ejecting a crazy-man president or one bent on establishing a dictatorship.
When a crazy-man has his finger on the nuclear button, there is no time to go through a long impeachment proceeding. Having a nation tangled up in a rats-nest of politics is easy pickings for Trump types — would be dictators.