Fighting wildfires is dangerous - fighting wildfires from the air is dangerous - fighting wildfires from the air in a narrow mountain pass, with high winds, low sun (6pm local) and no doubt clouds of smoke and retardant.....well...
A rough and ugly job, and my deepest respects to those with the skill and courage to take it on. But sometime it requires luck as well. And perhaps the luck just ran out.
We can hope the final report will clarify what went wrong and how.