I really wouldn't be so quick to judge Sprader, especially considering there is so little factual information on the incident available at this stage. Assumptions aren't worth much but one thing we can probably assume is that Sprader wasn't too enthusiastic about dying in the desert. It's not an easy way to go dying of heat exhaustion and dehydration. Many better ways out there to commit a suicide.

Hard to say but perhaps Sprader was simply a victim of the gung-ho mentality so prevalent in some branches of the military these days. Could be he realized he made a mistake and was desperate to set things right anyway, without waiting for rescue and admitting he was in a bad situation. It's happened before. Running around hooah in a hot climate will lead to dehydration very rapidly. A lot sooner than you realize. 90°F doesn't sound that bad but high humidity is a problem, maybe intense sun exposure, too. You can carry plenty of water but if you don't drink enough regularly you might still dehydrate in a matter of hours. At this stage you're going to be dizzy and even less capable of making rational decisions than you were before (and Sprader clearly wasn't doing too well in that department). Maybe he also had a health condition that we don't know about. Add anxiety, fear of ridicule by his friends, failing the test, whatever... All the little factors adding up. In any case, you can still die in that kind of situation even though it may look totally harmless to an armchair observer.