normally a back type blowing out would not cause a vehicle to spin uncontrollably.
I speculate the vehicle was travelling at high speed and the driver lost control due to erratical steering lose.
Having no seat belt on which caused him to bounce all over the place immediately, thereby losing his grip on the steering wheel.
If he wore a the seatbelt this accident could have been prevented.
It's not wearing the seat belt that contributed to the roll-over. imo