But slamming on your brakes like he said he did? Not generally a good idea.
At the time, the risk of getting rear-ended was less than the risk of that overturning trailer dumping tons of scrap metal on top of him. I’d say he did the right thing, given the circumstance.
I went to youtube video - he was along the trailer for quite a ways, then slowed down for a car in front of him, and the trailer on his right kept going. It looked to me that as soon as the trailer started going over he slowed down even faster (he didn’t slam on the brakes).
But then - he drives over to the left shoulder (to get out of the lane I suppose) but drives right into all the debris.
A person comes over and asks him if he is okay. “Yes - okay, but something wrong with my car - something is underneath it.”
(Well, um yeah...!)