Collapsible pin technology may have been helpful here. If the obstacle collapsed when hit, it might-might- prevent that rotational fall.
The horse would have rotated over that jump even if it had held solid.
I’m not certain I like the visibility of those fences- the horse comes around the turn and is totally unprepared for those particular jumps. My friend asked me to show her horse in a jumper class years ago. I had never ridden her horse before but thought I could give it a try. I had planned on being a spectator that day. Good thing I could fit in her show clothes. We did well except for one particular fence- had to make a tight turn around the corner and the mare was looking at a different fence coming around the corner so we ended up knocking the rail.
I don’t know why they have to hide difficult combinations around corners. Let the horse be able to look at the fence and evaluate the situation as they come in. The horse just looked totally unprepared for those particular obstacles.
I hope the rider makes a full recovery.