Everyone knows about stalls but there is a lesser known category of stalls that happens at high speed during maneuvers (turns and loops)... this is because the "angle of attack" (thus the "critical angle of attack" just before stall) is between "wing chord" and "relative wind" and not the "head wind"...
when a pilot tries to pull close to the bottom of a loop his/her plane (to level out) the wing is close to critical angle of attack since the "relative wind vector" is more from the bottom of the wing. The wing loses lift and the plane starts sinking in the loop... the only way to decrease the angle of attack here is to ease on the stick, or widen the loop, but the wider loop is not possible since the ground is fast approaching and if there is no altitude margin (this was an demonstration maneuver designed to wow the spectators so no margin here) a crash in inevitable...
Lift of a wing depends on (at current altitude) wind speed/direction, humidity, baro pressure, ambient temperature... Physics is brutal and the equation is dynamic... you set your loop decision heights and after that you are on a roller coaster that will follow the tracks of physics...
This was neither pilot error, nor it was machine error... an experienced airshow caliber pilot was rehearsing maneuvers to wow a crowd, margins were lowered and it was his day to perish due to an unsolvable equation...
I think he did eject at the last moment, hence the parachute deployment, saved his remains intact, quite lucky as the outcome could have been complete vaporization at a nose first impact...