He had gear on the direct variation to the left of and in between the two cruxes on MF. He then traversed right onto the normal MF route in between the cruxes. He may have placed another piece before getting onto the normal route. He then climbed/aided through the second MF crux with a nut that was not clipped, so from where he fell, which was above the second crux, his last clipped piece of gear was a ways down and to the left. My partner, who was above him, thought his leg got caught on the rope, but his leg may have been caught on a sling, or a feature in the rock, since he did fall over the prominent left-facing MF corner. Either way he got flipped upside down with a lot of force due to the length of the fall, and I think the fact that his gear was off to the side contributed to this type of fall. If that nut had been clipped he would not have fallen nearly as far, and would likely not have been flipped since his gear would have been directly below him.
Again, I don't want to place blame or judge here. Most of us, myself included, have probably made lots of mistakes while climbing over the years that could have ended in disaster. Instead, I'd rather systematically evaluate what happened to help make climbing safer, along the lines of the Accidents in North American Mountaineering reports.