the aircraft appears to have been in a stalled mode with tail down and nose up at first impact or to put it another way insufficient air speed close to the ground coupled to insufficient height to recover before hitting the ground.
One thing does surprise me. Why did the flight deck all succumb when they would have had full harness and more warning of the pending accident than anybody else? The cockpit area seems relatively undamaged.
You have answered your own question (also discussed at length in a previous post).
If, as seems to be the case, the aircraft hit the ground in a nose-high attitude with a relatively low forward speed, then it's simple geometry.
For everyone on board to have been subjected to the same impact forces (in this case vertical deceleration) then it would have been necessary for the fuselage to progressively collapse while maintaining the same nose-high attitude (think of a collapsing chimney). If, on the other hand the fuselage remains rigid and (relatively) intact, then it's more analogous to, say, a golf club or cricket bat striking the ground where one end hits first and the other end then accelerates in an arc to strike the ground with a higher velocity and consequent higher impact force.
So, all other things being equal, the nearer you are to the front of the aircraft, the more likely you are to be subject to an unsurvivable impact force, harness notwithstanding.