Rev nailed it.
I saw it back in 1983 at Leonard Wood. Only back then, Drill Sergeants did have the ability to get rid of the sick, lame, and lazy. We started off with around 230 and graduated 180 something. We even picked up a few along way. Guys that had gotten hurt or were getting a second chance because they couldn't complete some phase of training with their original company. Most of the former graduated; very, very few of the latter (mostly Basic Rifle Marksmanship failures, they just couldn't quality with the M16, even spending most of their days on the Weaponeer.*)
A Manning type, weak mentally, would have been weed out and TDP'd (Trainee Discharge Program) the first two-three weeks. That's when the Drills rode everyone hard, trying to get you to quit, to see how hard and how far they could you and you could push yourself. By week five, those who could hack it, were going to graduate, baring being a *expletive deleted*ck-up and not being able to shoot or complete the common tasks for the end of cycle test.
Yes, Manning obviously had/has mental problems. And most definitely should have been discharged in BCT. But the drive to keep up the numbers prevented that. Lowering the standards also enable people like Manning to enlist and get passed through BCT, where the weeding out should have happened., but didn't.
Does the Army (and US military) owe anything to folks like Manning, who joined with obvious mental issues? No, I don't think so. If I remember correctly about what they told us about TPD, was that it like you never joined. The Army owes you nothing, and it's not like you were given a BCD or General Discharge. It was basically "Thanks for Playing, you get no lovely parting gifts, just a bus ticket home."
* What made things even worse for those that NO-GO'd BRM was the fact that A) Most of the Drill Sergeants were Infantry. and even worse B) The cycle before us, every last swinging richard had qualified with the M16 on the first try. 100% GO. There was was this Red streamer on the Company Guidon that read "100% BRM". And our Drills were bound and determined to repeat that feat. When we didn't, not only did the bolos get absolutely smoked there at the range, but the entire company got smoked for the next week or so. My arms still ache thinking about how much time I spent with my rifle held out in front of me. It was like week 1 all over again. And those that continued to bolo got more hell, then recycled. It was only in week seven that we finally were taken off "Total Control", and the drills relaxed a bit. But man were they pissed when we didn't 100% qualify.