Trump and Patel have moved the FBI relatively more toward politics and optics and away from the criminal justice mission.
FBI agents were pulled away from their work to focus on immigration, despite that ICE got massive funding and a mass of new ICE agents.
FBI agents determined that people were peacefully protesting and that there was nothing to investigate. The Trump administration ordered them to investigate anyways.
Some FBI agents were pushed out or forced to quit on principle. These were trained agents doing their jobs well, now out of the agency.
The way Trump runs the bureaucracy is similar to how many dictators run their bureaucracies. He hires, promotes, and fires based on loyalty, not competency. Overtime, this makes agencies less effective, less principled, less competent, more corrupt, and more loyal to the dictator. This is how many dictators have ineffective governments, and their people suffer as a result.