This isn't Russian assassins. They kill specific notable people, not functionaries. Nor is this about not being able to talk about work. Working in these fields becomes your life. You talk about it all day. They don't want to talk about it more, certainly not at home. This is about over-qualification in a narrow field. These are people for whom there is only the one job. Then ... something happens that threatens that…
So he had no qualifications outside of intelligence.
Again, working in the civilian sector certainly means fewer pure thrills than working in military intelligence, but the professional skills are massively transferable to other contexts absent a dishonorable discharge. I find it much easier to imagine some issue that didn't comport with his whole-life military ethos - a personal failing, grossly anti-meritocratic discrimination, repeated subjection/exposure to unconscionable command decisions or somesuch.