This is the correct answer. When you drop off the bottom 30 percent of the population via the AFQT requirement (the part of the ASVAB that correlates well with IQ) you are getting rid of 100,000,000 nitwits. Further to those, you also get rid of the criminals, and psychos, and junkies. This makes the military a kind of modest elite. Their children reflect that and do reasonably well in school.

Are people with 125+ IQs enlisting? Not for the most part, but almost none of the 75 IQ people are enlisting, and they cause a wild disproportion of the problems in society.