We are one of, if not the, only country in the world that doesn't (until now) prosecute high level politicians.
This was a massive oversight of the Founders and it has led to incalculable damage to the country, the increase in corruption and expansion of centralized power.
The Founders were so used to the heads of monarchic government oppressing the citizenry that they couldn't and didn't fathom the heads of an *elected* government doing the same and using that loophole to cement its own power.
Expanding executive power to the point of shielding the executive simply because they are or were an executive is the recipe for dictatorship and monarchy.
The Founders left the door open to create the very thing they hated the most.