C-SAR, looking at the impact mark it looks fairly shallow. So the question is, was the first impact from the fuselage underside (where it starts to taper towards the tail) or from the actual tailcone?
I ask because if the first impact was from the fuselage underside, it suggests a lower angle of attack i.e. only a couple of degrees more than the tail strike angle of 15.5 degrees I referred to earlier. It also raises the possibility that the main landing gear hit the power line together with the fuselage.
Speculating further, a high angle of attack at impact may be one of the contributing factors to the high degree of destruction. If the AoA had been lower, the landing gear would have hit first and absorbed a lot of the energy that now caused the tail to break off and the airplane to do its final pitch down.