As a lifelong professional jet pilot I make a couple of observations.
- A runaway trim that is not detected(?) will put the aircraft into an uncontrollable dive - but NOT a vertical one.
- This a/c seems to have been just fine and stable right up to the point it left cruise altitude approaching destination
- The fact we are seeing lots of panels on the surface with pulled rivets suggests design forces were exceeded in flight leading to structure break up. The rest of the structure is in a very deep hole.
- No conclusions can be drawn from the FR24 data that a recovery was being attempted. This aircraft had departed controlled flight suddenly and catastrophically
For me the circumstances are very similar to Metrojet 9268 (EI-ETJ) that crashed in Sinai. When the four corners are established we may well find that the empennage is not located with the main body of the wreckage indicating separation. The list of causal factors for that separation at the end of a stable cruise is a very short list indeed.