any psychologists here, why is it that we now have several pilot suicides with many pax killed yet I have never heard of a bus driver doing a suicide and killing the passengers along the way?
You don't need psychology to answer this - merely physics.
Kinetic energy increases as the square of the velocity. There is every chance that a bus crash at 50 mph is survivable. An aircraft, at ~500 mph, has
100 times the kinetic energy, and if flown deliberately and directly at a mountainside, has
no chance of being survivable.
Hence, there is a guarantee that you cannot be held responsible for your actions
post-facto. A bus crash may only leave you badly injured - and still having to face the music.