I would take this as an example of why it pays to do things correctly. Not knowing all the particulars, the driver just may have had his ducks in a row. Someone might well have cut him off and when the driver reacted, they may well have just lost it.
In looking at the video, I would have had the machine chained differently though it stayed with the trailer. It might have shifted backwards some when the trailer flipped.
I know of one last summer/fall. Guy was taking his newly restored tractor to a show and ended up exactly like that. He got cut off and lost it. Tow vehicle, trailer, load, securing devices were all in order.
To bad, did a number on his nice tractor too.