So you’re saying that since it was a controlled descent, that would indicate that the pilots had the wherewithal (oxygen in case of depressurization) to initiate such a descent. And if they had the wherewithal to initiate the descent, why didn’t the descent stop at 10,000 feet or whatever altitude was necessary to clear the mountains.
Exactly. A controlled descent could be on autopilot or hand flown. If on autopilot, it would stop at 10,000. That means the automation was off if the crew was unconscious. That makes no sense.
I think there are only a few explanations:
1). Someone in control that wanted this to happen.
2). A fire and/or smoke at altitude, that incapacitated the crew AND the automation (electrical fire is a frightening scenario).
3). Structural failure at altitude, disabling the crew and automation (bomb or airframe breach in the nose).
I think #3 is the most likely now, but we may never know because of the more political way of accident investigation since TWA 800.