Snipped by me.
Not aimed at this post or any comment in particular- I just wanted to add some additional context to the fact he decided not to finish his PhD and am using your post as a launch point. There are estimates that 30-50% of people do not finish PhD programs. Some may not pass all of the different qualifications or examinations, but others just choose not to finish. PhD attrition a big issue in research and graduate education. By all accounts we've seen so far, he chose to leave. This alone is not a red flag to me. His advisor's comments make me think it was not a red flag to anyone there, either.
It is also my understanding that he graduated with his Master's just over a month ago. While we could criticize him for not starting his job search early enough that he had a job lined up, if he waited until after graduation to start his job search, it's unlikely he'd be employed by now. He might have had edits on his master's' thesis to finish, or if he had completed enough research, he might have a paper he was preparing for publication. His lawyer claims he has been looking; maybe that will be relevant to the case in that they will say why would he jeopardize his plans or something of that nature.
Additionally, mental health is a real concern for PhD students. According to a recent paper, 1/2 of PhD students experience psychological distress and the prevalence of mental health issues is higher in PhD students (paper here:
http://www.sciencedirect.com/science/article/pii/S0048733317300422).
It's hard to tell the cause and effect here, because IMO, research attracts some people predisposed to some mental health issues (research is an easy place to stay isolated, etc.) in addition to the fact that academic pursuits can lead to anxiety, depression and other things in students. I'm not saying he necessarily had any particular issues or that these are responsible for what he did- just the reality of graduate school.
Other information:
http://www.sciencemag.org/careers/2017/04/phd-students-face-significant-mental-health-challenges
https://www.theatlantic.com/education/archive/2016/07/why-do-so-many-graduate-students-quit/490094/
http://www.chronicle.com/article/PhD-Attrition-How-Much-Is/140045