That last sentence, especially the bolded part, makes me think they died because they were thrown around in the vehicle after the collision, indicating that they weren't wearing their seat belts. The only person in Princess Di's vehicle who survived was the young body guard, who was wearing his seat belt.
In short, it doesn't matter how well built your vehicle is, to avoid the frequently fatal internal collision that often happens after the external collision, the best thing each of us can do is wear his or her seat belt at all times.
This was on the local news yesterday morning, (KGO, I think) and reports stated that the deceased were all wearing their seatbelts.
They could have been wearing seatbelts, it's a terrible secret that many brands of SUV's don't have roofs that are strong enough in a roll-over and they crush back in on the occupants. Phoenix news did an indepth report on this recently because of the number of deaths from crushed roofs, it's very technical, has to do with weight ratio's.
All other local reports state that all occupants were indeed wearing their seatbelts.