Ok, so the truck recording was headed northbound on 421. The truck that crashed was heading eastbound on 74.
The Google map appears to be a bit obsolete, but shows what the terrain was like a few years ago.
The Mapquest map is newer.

How fast was the truck going? If it had hit the 421 exit, it should have been able to hold the curve, and stop before getting to 421. The "old" 421 exit likely gives a nice slope (ramp) up to the overpass.
I can imagine a truck swerving, a bit, but I still have a lot of troubles imagining how a driver could have made that jump awake and sober.
Actually, I74 was going around a gentle left curve.
The offramp took a gentle right curve.
The truck went straight between the two at a high rate of speed without braking.
That sounds very suspicious for driver error or sleeping behind the wheel.
It would be interesting to see an analysis of the truck tracks and skid marks.