I suspect it was a traffic fatality and will revert to the State Troopers.
It is likely the man was driving so fast his clothes were blown off and during the process he lost control and turtled the truck
Clothing isn’t going to get blown off inside the cab of a pickup truck, even at 120 with the windows down.
He was driving around nekkid, whether that was due to some sort of fetishy sexual kink or drugs will be established during autopsy.