I have read the 32 pages or so of this thread with interest. Some good info,some drivel & a few good theories expressed. I am an A/C Engineer so I am not going to speculate on the exact ins & outs of how to / or not fly an A330, but consider this as a possibility of what happened.
The 3 pilots study there WX briefing in RIO prior to Departure and decide that the WX enroute for the proposed flight plan is not expected to be outside Normal operating limits for the A/C ( It is another conversation to ask how accurate the WX forecast actually was but time will tell when the FDR is downloaded)
The A/C departs & flies on the sheduled route for approx 3 hours uneventfully at night.
I have heard of a case where severe Lightening Bolt punctured the Radome & Disabled the WX Radar antannae thus disabling both radar systems on the A/C - maybe this happened in this case also.
So the crew are now flying with no WX Radar at nite using a WX forecast at least 4 hours old. During that time the storm intensitys & Locations may have increased & changed location. Maybe the crew decided to turn back & hit one of these large storms head on & the extreme wind Forces inside the storm tore the A/C apart.
Does this sound like a realistic possibility to any of you guys who actually fly in that part of the world?