UTV pumper unit burned up during escape fire incident

The photos accompanying this report of an escape fire incident are surprising and instructive. Who knew a UTV could be so flammable?

Screen shot from the Facilitated Learning Analysis of the Cold Brook (S.D.) Escaped Prescribed Burn.
The UTV ignited within seconds of the crew escaping after it rolled.

The fire escape (which turned into a wildfire) occurred on April 13, 2015 during a 1000-acre prescribed burn within Wind Cave National Park in South Dakota. The details of the burn, and extensive analysis, are given in the link posted above.

The burn unit consisted of grass understory with some brushy components along with dense and open ponderosa pine stands. The area where the UTV incident occurred was almost solely grass. Although green-up had begun, it was still early in the growing season, and most of the fuel was fairly tall well-cured grass. The objective of the burn was to reduce thatch and to kill seedlings and pole size pines.

The escape occurred when sudden wind gusts accompanied by a dust devil picked up fire and carried it across Highway 385 into a large site that was not being burned, but had the same fuel character. (A video of the development of the spot fire is provided in the report.)

When the escape occurred, two UTVs were sent to control the fire. The UTV that was to come to grief crested a mild slope and was surprised to find the fire ahead of it and below. It quickly circled to get out ahead of the flame front, began a slow-motion movement along the side-slope, and tipped, coming to rest on its right side.

Both the operator and passenger quickly exited. With the UTV on its side, the pumper was no longer working. Fortunately, the crew found an escape route safely into the black. According to one crew member, the approaching fire was very hot and the "UTV torched right away".

There were some indications that the weight distribution and tank design made the UTV unsteady. In addition, the operator was unfamiliar with the power steering with which this (Polaris) UTV was equipped, and oversteered, thus causing the UTV to tip on its side.

Seat belts were present in the UTV but neither person was strapped in. It is likely that if they had been strapped in, they would have been burned up along with the vehicle.

Why did the UTV, which is mostly metal, burn up?