Looks like a wind gust or ineffective aileron deflection failed to compensate for her weight and get the wings level for the inverted pass. Not enough altitude to correct so all lift was lost and it nosed in left wing first. Very sad and tragic.
One of the reasons I never go to airshows, even though there are many here in Florida. I really don’t want to see anything like this (although I realize there are others who are hoping it will happen).