It wasn't the Falcon, it was that other model that fell on it's behind. McNamara was a graduate student and Fellow at Harvard teaching statistics when the war broke oth. Dean Dornan sort of voulunteered McNamara for the defense department. Basically, Dean Dornan wasn't unhappy to see McNamara go and found a way to ease him out the door. McNamara went into the army with the advanced rank of captain and taught short statistics courses to DiD personnel in this country and in the UK. He was promoted to Lt. Colonel before leaving. He never picked up a rifle or saw action during his tenure.
If you look closely at McNamara's background, he was a blowhard with an agressive intimidating manner beneath which was very little talent.
McNamara was also rather far to the political left. He was a Berkeley graduate and is described in his own book, In Retrospect, as being an admirer of socialist Norman Thomas. That's one of the critical keys to understanding the real McNamara sympathy and commitment.