Lessons that are obvious without speculation
Instead of speculating as to why, dare we look at how?
This airframe did not slide down the run off area embankment- if it had the resultant effects could have been far more severe.
However of note, the structural failure above the wing seems to centre on the wingbox, gear beam area and runs very nicely up the seam of the overwing door frames, then turns thru 90 degrees to a very nice clean line at the manufactuers tear strip/section join line.
So heavy vertical loads through the gear and cross beams may, may, have set off this overwing snap.
The rear end fracture is altogther more interesting, its snapped up near the thinner area just before the pressure bulkhead and it appears the fin and rear end have continued to travel forwards -underriding the mid section.
If it did get briefly airborne (pure specualtion by others) then one is reminded of the EAA Super VC10 accident - where the commander decided not to take to the air with an unknown condition - and settled back down.If the run of area had been flat and fence less, the resultant mess would not have occurred.
What is clear is how lucky we are that the Kallita machine did not slide off the embankment- just as the Iberia A340 did not- at Quito - but AF did at Toronto.
My point?
Run off areas folks- the are still not what they should be - flat or with catcher pits and fences.