There is another photo that shows a long draw bar or extension. I did some math in another thread and it increased the torque on that hitch damn near 50%...
Using a normal bar and 375# of ball weight, he should of had something around 300lbft on that hitch assembly. I guesstimated an 18" extension...it was close to 600lb ft of torque on that hitch assembly (more than 500# / 420lb-ft with a normal bar).
I feel for the guy, but that tongue was too long and I'll bet that tongue was far more than 375# when it happened (especially since it was weight at the dealer).
We can see 2 jerry cans (80#), a rotopax (40#) a propane bottle (30#), a metal box (40#) and I likely one or two batteries in that tongue box (100#)...plus whatever is in that trailer. Some of that weight is divided between trailer and tongue, but I'll bet he was close to 500# of ball weight.
That may be a weak point in the frame, but he was too fast and to heavy for the conditions. Let's not forget chevy reduced the towing capacity by almost 2000# for the ZR2 ... Citing offroas (softer) suspension.