What is the “deep state?” It is all of the people who were hired at the federal level to provide expertise and to enforce the law equally and predictably. It includes the military, law enforcement, the judicial system, and bureaucrats of all kinds.
What Trump calls the “deep state” is a formidable barrier to the exercise of arbitrary power for the benefit of himself and his reactionary supporters and the detriment of everyone else. It relies on knowledge, precedent, and written law rather than the whims of a despot. It is the child of the Enlightenment, not the early Middle Ages. That’s why Trump hates it so much, and why his platform for 2024 will be to destroy it.