Maybe this guy has Vitterman syndrome, only really upset that the higher ups didn’t listen to him.
I think you may be on to something. It might just be he was not happy what track his career was on and decided to pull the pin. He’s certainly a legend in his own mind.
I suspect the guy didn’t object to the fiasco that the evacuation of Afghanistan had become, but that the U.S. was leaving in the first place. That would explain any resentment of Trump.