I almost hate to post this,, but, what the heck??
If you think about it,, having the tractor "move" during that collision may have been safer than having the tractor rigidly connected to the trailer.
When the tractor was moving, it was slowly reducing speed.
The tractor used the rear of the pickup as "crumple zone"
That is the same results that car manufacturers achieve by designing in "crumple zones".
If the tractor was rigidly connected to the pickup truck, during the collision, the mass of the tractor would have kept the velocity of the pickup higher.
If the velocity of the pickup does not reduce, the pickup /car collision would crush more of both vehicles.
If more of the pickup is crushed, the occupants of the cab will sustain more injuries,,,
Yes, my example is very dependent on this exact situation,, but, many people call that ,,, LUCK.
These are pretty nice dump truck crashes,, I like the one where the truck goes over an embankment,,
Hmmm ,, maybe the cannon firing the cannon ball at the front of the moving truck?
(why is the paint inside the bed not scratched on any of the trucks??
)