Why did the Founding Fathers put that in the Constitution?
Did they not realize that a corrupt crooked criminal would use that out to pardon other corrupt criminal crooks?
Did they really think having a check-and-balance system consisting of THREE EQUAL COMPONENTS would take care of any charlatan scam con snake oil salesman from screwing the system and mocking it and ridiculing it and undermining and sabotaging it?
They were not as smart as we thought they were. You ask "who could have manufactured a powers that be anywhere but in fantasy?" Smart people are supposed to plan for ALL EXIGENCIES aren't they? Even the most bizarre and unlikely. Have a plan for it JUST IN CASE?