It's not really the qualifying (or lack of qualifying) that got him in trouble, it's the falsification of records by his subordinates that made him vulnerable.
Someone was out to take him down and he should have CYA'd himself.
From the sounds of it, someone who didn't like him taking mostly republicans with him on this trip...
But then again, someone who knew the inner workings of the army, his staff and his qualification was in on it.