Classic loss of concentration/dozing off accident.
You hear the rumble strips on the right, and you jerk the wheel to the left. Next thing you know, you're off the road on the Left. Good thing there was a guard rail.
Full rollover, back onto the wheels?
Could have been a crosswind.
I’ve seen semi’s flipped in Wyoming
” Good thing there was a guard rail”
I think the guard rail led to more injuries and deaths.
Back to my original thought:
What guard rail?
My uncle used to drive a tour bus in this area when he was young. He once told me the winds could be treacherous, bus this looks like a relatively flat stretch of road, not a box canyon or anything steep. My bet is driver error as well.