Someone in the reddit thread guessed that maybe he answered something in a way that's not just wrong but like super illegal in a "you're stupid enough to be more of a liability than a help" kind of way. Like outright saying "yes i want to go overseas to murder people" sort of answers.

Being low test scores isnt a permanent disqualifier, they can waiver you in if you ride the line. something medically most likely. Probably too much water in the brain