Looked like it maybe was a black out from excessive g-force on the turn, the P51 went stright in at an angle of about 70 degrees, no trailing smoke, no parts of the aircraft falling away before impact,appeared too be at full throttle.Unless the control systems went bonkers, I would guess the pilot blacked out.
Horrible accident, the V-12 engine block went cartwheeling away.You can see it in the video.