It's a fair working assumption that the bodies which have been found so far were at some point thrown clear. This would have had a far better chance of happening if they were not strapped in. If the captain was in the cabin when the event happened he may have tried to get back to the flight deck, but got pinned down by heavy g's. This would also account for him being found with a steward and not another pilot. Typically, the tube breaks just forward of the wing spar when bent enough - that would be the area where the cabin crew rest bunks are located.
If the assumption about bodies being thrown clear is correct, then more than 50 people were not strapped in, or were out of their seats - 25% of the loading - a fairly average number mid-flight. This would also point to a sudden event and not a gradual deterioration. Again, the sudden g's would have prevented any return to seats.
The SATCOM/ACARS could have continued functioning for a few minutes after the aircraft had already stopped flying, giving the potentially false impression that pilots still had some control.
It is very tempting to continue speculating - in 2000 posts somebody has probably got it right - but a line needs to be drawn between trying to interpret what data we have, and just thowing out blind theories.