I know it's the usual speculation, but IIRC in most nose over accidents, the fin collapses, and traps the pilot in a very bad position, bent over in a position where breathing becomes very difficult, or even impossible, e.g. Paul Morgan in his Sea Fury at Sywell a few years ago, Skyraider pilot in the States at an Airshow, a Harvard in the U.K. I would suggest that this may well be the case here. Sadly, all life has a risk element to it.