He was probably not heat acclimatized and attempting to run across the basin (lowest point in US) about 6 miles in 123 degree heat with not enough water. He probably didn't realize the basin floor was not solid and had to go around. He was not equipped to survive (knowledge, conditioning, gear).
Dying of hyperthemia is quite a nasty way to go. 123F is absolutely brutal and most sensible folks (along with the wildlife) would be just looking to seek shelter, water and to radically reduce activity. Going for a middle distance run with limited water in such high temperatures is pretty stupid now matter how excellent the athletic ability is. Solar Radiation physics doesn't care! Even then there is probably a point that the bodies thermo-regulation can't even cope no mater how much water is available without a breeze and suitable shade to aid evaporative cooling. Temperatures above 90F generally need careful consideration especially if air humidity is high.
Even a carrying a Lightweight reflective umbrella such as a Swing Liteflex Lightweight Trekking Umbrella UPF 50+ for shade could have made the difference between survival and death.
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