What kind a suicidal person would take everyone else out with them, unless they were a terrorist suicide bomber?
Well -- kill two birds with one shot or rather a flock of birds one shot.
By doing this he gets back at his wife/exwife as support payments to her are gone, and his financially troubled employer who had probably been putting the squeeze on the pilots -- particularly the older ones, and the Malaysian government for convicting a friend of his.
He deaded a lot of people with this move.