I do not believe the founding fathers were all seeing, nor heroes either, but men with a vision, who were well compensated for their time, they saw to that, beginning a long standing tradition of pocket lining.
The first to digress from the plan, was the architect himself, Thomas Jefferson who broke the intended tradition of one party, two candidates, second place gets a useless but highly paid job. He formed a second party and campaigned for four years after having been snookered in the first "stolen election" which he had not foreseen.
I do not believe they foresaw how deeply would the courts become law makers, and never foresaw the on-going concentration of power in the presidency.
So in answer to the question of when the departure started...right at the beginning when Mr. Adams conspired with Mr. Washington to create dynasties.