engine mounts
BAT had a fast airframe, unlike other C210s, that just don't want to pick up speed. It was a workhorse, with Sefofane for more than 10 years, but I don't think it had an overstressed frame, that would brake up while innocently flying along while everything is in the green...
Somebody else mentioned that the pictures looked like the engine could have come out of it's mountings in flight and hit the wing. Possibly a stone chip on the prop caused a piece of the tip to come of, causing an inbalance, that in turn made the engine rip out it's mountings?