A post-mortem examination confirmed he had suffered several potentially fatal injuries, with a massive brain injury to the right side of his head.
While he had not been wearing a seatbelt, Coroner Carla na Nagara could not confirm that this had made any difference to whether the death could have been avoided.
The post-mortem also revealed that Stantiall had been eating at the time of his death and chips and dip were found in the cab of the ute.
Senior constable Greg Taylor of the Tasman District Crash Investigation Unit said there was no evidence of any vehicle fault or road fault. He also concluded that speed was not a factor.
The coroner concluded that momentary distraction had caused the accident.
"Quite possibly due to reaching for food/eating - Mr Stantiall found himself having to make a split second decision to avoid collision with other vehicles," na Nagara said.
She noted that of the three options Stantiall had, he took the one that posed the most danger to himself and the least to the other road users.
"Tragically he was unable to control his vehicle on the grass verge, leading to the fatal impact with the tree.
"The case is a startling example of the devastating consequences that can follow momentary distraction while driving," she said.