He did not have a history of juvenille delinquency or below average intelligence. He was a 39 years old career Army officer and a physician who must have undergone batteries of mental evaluations thruout his military life. So, I doubt the weak character argument will be very convincing.
my point is more specific than that generalization. In none of those 39 or whatever years the Islamic life angle was put to any stress, until it was time to ship out.
So yeah, he would take all the stress and strain of med school because there is that big payoff awaiting, he'd go join and train in the military because hey, he doesn't have to worry about filing insurance claims for patients....but when it comes to actually going out to go treat and save some lives of fellow soldiers, that's too much for this guy. Oh yeah, some character