Basic training ain't some magic bullet. Sure, they're more mature as they've been through something and have learned expectations and responsibility and they've damn sure learned work...
But they're also programmed in a certain code.
I've never drank harder, worked harder, lived harder, and loved every second of it as I did in the four years following bootcamp. First term Marines are known for good reason to be the glorious bastards they are.
It's easy to forget they are programmed. I turn 50 soon, and to this day a certain command issued in a certain way gets a predictable response from me. Not near as instant to react to it, but just as instant to recognize it.
It's about control. Within the ranks that control is crucial to mission accomplishment, and mission accomplishment is the absolute priority of any Marine no matter the rank. So is responding and adhering to recognized authority.
It isn't until much later in life a person grasps what they've done at the behest of authority and by authority with no skin in the game and often for purposes that were less than respectable..... this is a recent issue, though, and goes back to "last 50 years" sentiment. I dont think it was a thing prior to Korean War.
A matter of fact, any DI will tell you third phase recruits are uncontrollable and dangerous except for the fact they THINK they're operating under strict guidance. Sorta like an elephant tied to a post with twine. This is the condition wanted in combat situations- and can be achieved quickly with the right motivators and because of programming.