Don’t know much deep about these things, but i do know that there are set parameters of thrust where one should perform so n so maneuvers.
But upon viewing the video again and again, especially this one
Pilot error seems the best explanation and it is inter related with engine.
Notice when the aircraft starts to lose altitude and a second later you hear less engine sound but just the drag (speed of sound vs speed of light, stall first, sound disappears later), at the last quarter either engine wasn’t working or maybe the Maneuver had
a toll on the pilot, (unconsciousn)