It appears that he was landing in some uneven terrain in the main valley... in a flatter area before the foothills rise up to the mountains. It looked like he was on one side of a gully. The 180 flipped and there was a fire.
Even in open terrain, with no snow right there, it took two days for the plane to be spotted.
There's a lot of speculation now about engine problems, etc., but of course no one knows at this point. It's sad and sobering when such an experienced pilot (over 20,000 hours), in his own airplane, can come to this point.