Lucky man. He did well to pull it up, but I wonder if he touched the rear brake in those final moments, creating that caliper damage.
Looks like a spoke falure to me. It's amazing how quickly they can fail, once one or two let go. Some riders zip tie where the spokes cross one another to reduce damage from a failure. Many of us forget to tighten & re-torque the spokes - all the more important these days on our potholed roads. Sometimes the rims themselves crack too
Catastrophic wheel failure always makes me think of that Robert Dunlop crash on the IoM.