It could be just about anything, including the incredible stress, or the back biting within the agency, or it could actually be because of something within his family.
FNC said that Tenet had wanted to leave for a while but the administration urged him to stay.
You're one of the few who agree with me - Tenet will be loyal to the president and country. Given the president's father's background with the CIA, I think there is loyalty on all sides in this issue.
Normally, this would be a reasonable argument, but we are dealing with, at best, a RINO of Specter-the-defector stripe. And as a Clintonite, more likely a Fifth Columnist who went along with all the insane Gorelick rules, and implemented the stupid destructive attacks on human intel.
We have another example where every word you just wrote could be said EQUALLY of Richard Clark. He was the 'Terror Czar' going into 9-11. EVERYthing he asked for he, in fact, got. GWB keeps him on when he could have made him a scape goat, and fired him for his flagrant incompetence, but he is kept on, but quietly demoted horizontally. He leaves, and as the story goes, 'the rest is history'. Tell all book, duplicitous 9-11 testimony tailored to be damaging, and his own staffers working for Kerry as Intel advisers.