I think it was the PTSD that led him to make-up stories when he got home. He maybe didn’t even know he was doing it. I read another article that said that maybe since he was such a big hero during his time in the military, he felt the need to continue being the larger-than-life hero when he became a civilian.
The real question is what is it that motivates denial of a report like this in the absence of confirmatory evidence?
Bingo! At its simplest, just another man who could not handle success and its expectations. We wanted a hero, we made a hero, his tragic end elevated his life to a God in a Greek play. Now let's run for cover as there are a LOT of keyboard commandos who only watch TV and they'll be coming with blood in their eyes.