BB said:
I am saying the cause might well be something that unlikely: something nearly impossible, yet NOT impossible.
AMF said:
Basically, high altitude flying is potentially one of the biggest can of worms in aviation.....high altitude flying in severe weather quickly opens it, and nothing on the aircraft need be broken or malfunctioning for it to be perilous.
(emphasis added)
Based on the discussion here by AMF and others, impassible weather is not uncommon in the ITCZ. This weather may have been impassible by any aircraft, especially a high and heavy one. If so, the most important question is "Why did the pilots fly through the weather rather than deviating around it?" The answer might be a nearly impossible combination of events or it might be something mundane and all too possible.