Hard to tell if he bumps the leg, or the cross beam. Either way, looks like an accident was bound to happen. Looks like it is just the uprights, and the cross beams. nothing connecting the cross beams front to back. Pallets are just held by the front, and rear edges. The cross beams are likely near their max weight, and the uprights do not look like they have extra strength to spare either.
If all the uprights were bolted down, they are likely just 1/2" anchor bolts. I doubt this would be different if they were bolted or not. If the upright was hit by the wheel, it would either bend inward if not bolted, or just buckle if bolted, same end result either way. If it was the cross beam that got bumped, it just pulled both uprights inward, and then they buckled, with the weight of the falling pallets adding to the cross beams buckling.
It may have been within the weight the racks were designed for, but there was no safety factor in the design.
I think the rows should have been interconnected, so they could still stand if one side of an upright got taken out.
Surprised they were allowed to get away without big bumpers at the corners of all the racking.
When I lived in Pa, I watched a big warehouse get built. they assembled the racks first, 60 feet tall, and covered several acres. Then the roof got built with the racks for support, and the walls attached to the outside. One big mass of steel racking, with walls and a roof.