Cleanup of 5th wheel accident in California

Not going back to re-read the updates after watching the video (was a quiet morning here yesterday so I got to watch the whole thing), but there were some comments attributed to (second-hand comments?) that he got hit (rear-ended?) in the intersection. I didn't see any evidence of damage to the rear of the trailer ... hard to tell about the truck, since the trailer ran over the passenger side and the truck was sitting on the driver side, but once righted, I still didn't see any obvious evidence of a collision with another vehicle.

My armchair quarter back guesses are the trailer brakes where not set up properly and didn't apply adequate braking power, and the trailer ran over the truck. Did anyone notice skid marks in or before the intersection?
???