Another power level time.
Honestly? I don't know anyone whose went to grad school who didn't have at least one category 5 REEEEEEE moment. Even the most collected and together students will do something weird at least once due to the pressure. It's really hard to explain. One of the most mature dudes I knew threw a statistics book at the wall because "none of it made sense". Going full retard is literally par for the course no matter what your major is. You will be stressed. You will consider quitting. You will be forced to lose your social life and lose sleep. It's hard because it's supposed to be. It's the Academic version of the military.
Imagine working an entire year on something and then you find one problem that nullifies
all of it
this literally happened to me. That's research baby! It's a cruel (but very rewarding) Gold-headed mistress. You just have to shrug and take it in stride and keep going.
Likely, Duke likely saw him going full retard and was like "yeah that happens" and looked the other way. They shouldn't have, but they likely did. In the least, they might have said "You should check out our mental health links or use the psychology grad students lab for help

". Which only people who are self-aware of their issues do. Schizo stuff kind of renders you thinking you're always objectively right so he could have gone or could have ignored it seeing his colleagues also having a retard moments and thinking it was normal.
I don't blame affirmative action for his entire grad school experience. I hold grad school for being how it is and Duke /his advisors partially responsible for not intervening when he clearly was struggling. They had
6 years Philosophy Ph.Ds take minimum 6 instead of 4 to notice something was wrong outside of the normal grad student moments and to get him help. There's programs and policies in place with most universities where for mental health reasons you can postpone your doctorate, go get help, and come back with no progress lost. This should have been him.