No way was this a mechanical malfunction. If you study the flight path of this aircraft it went down in the worst possible place for finding the fuselage (open ocean and the ONLY place along the entire flight path where the ocean was the deepest). This is NO coincidence and defies statistical probability for it being a mere malfunction.
Thanks. Agreed.
The question is really how and who.
I would take a good look at a stewardess who posted a picture of her wading out of water dragging her flight bag. That is a little beyond weird.
As for the pilot being the bad guy....maybe.
But there are several cases of pilots who intentionally crashed airliners and none of them used a bomb.
My guess is that it was a person who had no control over the aircraft so a bomb was required.