Has anyone considered the following scenarios:
Explosion destroys Fly By Wire signals to elevator and rudder, causing control surface run away to extreme travels, resulting in structural failure of the empennage due to huge aero loads.
or
Hydraulic lines are severed to elevator and rudder servos, loss of pressure allows the control surfaces to flutter, as they are now not held "stiff" relative to the HS and VS. Remember that these surfaces are not mass balanced, relying on hydraulic actuators to prevent flutter.
Or a combination of the above?
Notice that both elevators and the rudder came off, suggesting flutter. Elevator flutter would also be a reason to lose the HS halves as happened.