Any problem with the trim or elevator at high speed could cause this type of crash, so it looks pretty obvious to me that this was the cause. The tail wheel seems to back that up. I'd also have thought that a sudden unexpected 10g climb might not only put your lights out but also break your neck whether 20 or 80 (in my limited aerobatic experience of not exceeding 6g). It is a testament that the wings didn't come off.
How many G would be required to pop the tailwheel out?