Let's leave the diagnoses to the doctors please. The guy was public about being under a lot of stress and that's fine and salient to acknowledge. But it's misleading to use medical terminology unless you're actually his doctor and have evaluated him following the protocols of your profession.
Which we know you are not -- if you were -- you would be bound by patient confidentiality, and not posting a diagnosis here.
So just say his job performance was suffering and he appeared to be stressed. Don't medicalize it.
I am "evaluating" him as someone who feels he has come unglued in a similarly severe but less public way and recognises a fellow traveller. I'm fully entitled to say this, am I not? It's just my opinion.
I am not "medicalising" it — not least because the medical profession does not recognise burnout as mental illness (because it gets it backward and assumes it is an occupational health issue).
I am saying he is, to me, evidently mentally ill in the way I feel I have been mentally ill. I wouldn't accept a doctor telling me my problems are work stress.
"His job performance was suffering and he appeared to be stressed" is IMO classic American-influenced minimisation of middle-aged male mental ill-health. I would be shocked if what is going on is in any meaningful way limited to his "job performance" and that apart from the job everything else is going fine.