Maybe he was too low at the top of the loop. There is no wing rock or flutter in a high-speed stall, just loss of lift and a high sink rate. He was nose-high when he hit the ground.
Yes, nose high. Sad.
Been there myself, nose up, flyable airspeed, sink rate none-the-less. . .but not stalled. . .barely missed the ground, kicking up dust-devils when the sunk rate stopped and I flew up ad away. . .
Still have no idea what you mean by ‘high speed stall?”
A stall among aviators means something specific, and certainly not what this pilot was experiencing. He was not stalled.
Cheers,