Pilots are meant to be a trusted profession, at times making it into the top 3 on the “Most Trusted Professions” list:
Psychopaths will not take their own life, they take the lives of others. History has shown some of the most ruthless killers have been well respected and educated professionals. These individuals have the ability to change personalties and suppress any guilt associated with heinous crimes.
It appears this individual had some personality traits that may have raised concerns, but he crafted his skill well enough to be promoted into positions of power.
I'm sure now we will hear more about his past, and the red flags that were ignored.