I am a NCO in the reserve. I am speaking from experience and I can add that I am not arguing I am smart and others are stupid.
Note, that my emphasis is on the system that make people behave strange.
It is somewhat ironic too, since being a soldier exposes you to so many practical and different problems that are so different each time that there is no room to be actually stupid.
And I am not talking about combat, but mundane stuff like, tying a rope between two trees to hang wet cloths on. In normal life people that would fail at stuff like this can get routine and hide that they can't do such tasks without messing up, but soldiers do so much different things that they don't get routine and if you are a bit off you are exposed.
If you are the kinda guy that can tie ropes between trees to dry cloths on, the military structure makes you behave like you would have been "stupid" in many situation that only is a problem because you lack power.
So Soviet or American sailors, that wanted booze but had no way to get it, solved it in the way they could. In civilian life they could just not have put them self in the situation where they couldn't buy booze.
Hazing is maybe a big problem since you are locked in with some jocks you can't escape since the front gate is guarded by MP.
Simple as that. The limitations make you stupid.