After 30 years of Air Traffic Control experience, most as Tower Watch Supervisor in the USAF, this was a Pilot Error Crash.The pilot came in too steep, with too much airspeed to bleed off, so he put it into a stall position to get rid of the airspeed.
But he stalled it out and got lucky that he belly landed it into the underrun, and the closed portion of the runway, before the landing threshold and leaving a portion of the tail in the bay.