Don't rule out that it may have been a technical malfunction. Somewhere it's stated that it was 14 minutes between the disabling of two different systems. An electrical problem that resulted in a fire may very well be the culprit in this rendering the aircraft without any feasible means to communicate and navigate.
There have also been speculations about structural failure causing decompression.
Until the aircraft is found we frankly don't have a clue about what happened and everything is speculation. It's always easy to blame the human factor.