Reading todays papers or rather between the lines of todays papers
This would appear to be a depressurisation or un commanded severe pitch down which could not be controlled or some sort of structural failure which lead to an inability to stop the aircraft descending.
there are two things which would indicate incapacitation of the Pilot/pilots
Firstly the track of the aircraft was fairly straight which indicates it was under some control (autopilot) with no pilot intervention and secondly the lack of communication with ATC from the crew.
Had this been a structural or uncommanded rapid descent with alert crew there would have been plenty of time for the crew to have relayed their problem and the track would have unlikely been straight as the crew tried to regain control.
As the authorities have discounted foul play this has to be incapacitation which I hope is the case as those poor people would have known little about their impending fate I hope (( and that fact may give their poor relatives a small crumb of comfort.
Why the aircraft failed to level at 10K is another matter