Delegating power to regulatory agencies also has nearly nothing to do with Congress's recent gridlock and ineffectiveness, or the spate of executive orders that has prompted.
Between about 1985 (Chevron) and 2010 (the populist movements in both parties), this idea was at its nadir of popularity. For the entire rest of US history from 1776-1980 and 2010-2025, a distrust of a large executive branch was very popular, and pretty much bipartisan most of the time. Just because you do not remember a time when this idea was popular, it does not mean that it was a fringe one only until very recently.
Congress is designed to be gridlocked. That's its natural state. We are now learning why it's a good idea to have a relatively ineffective government.