I have made a little comic below to illustrate my thoughts.
I understand that the top of the fuselage near the tail section is on a “pull” load, holding the nose up, whist the underside is on a “push” load, see arrows. (sorry, English is not my native language) What do the stress engineers here think of the following thought: We know there has been a fire in the hold, for whatever reason. This would damage/weaken the structure of the lower part of the fuselage. With the tail pushing down the floor crumples up, the stress on the rivet-joint of the top of the tail section to fuselage is too great and rivets sheer off leaving a large gap following the loss of cabin pressure etc. Depending where the data and power cables for the black boxes run, this could be the moment where these are damaged. Before or during this process outer panels are ripped off from the fuselage hitting the HS etc.
Now, the question is: how do I insert a picture....
Hope this will work