Here's a relevant quote from January 17, 1961, from a guy who knew first hand what we now call the "Deep State":

"In the councils of government, we must guard against the acquisition of unwarranted influence, whether sought or unsought, by the military-industrial complex. The potential for the disastrous rise of misplaced power exists and will persist. "
Dwight D. Eisenhower

The Deep State is a fact, not a "conspiracy theory".

The derogatory utilization of the terms "conspiracy theory" and "conspiracy theorist" was deployed as a psy-op tactic by the CIA in the 1960's, to disparage and discredit critical thinkers who did not blindly swallow the US Government's "official" propaganda, such as that Lee Harvey Oswald was the "lone nut" who killed JFK, when CIA-designated sharp-shooters (note the plural) were the actual assassins.  It has been so successful in "managing the sheeple" that it is a very widely and frequently used tactic to cover up criminal government actions.