Nonsense.

You didn't know this person at all, and I suspect you aren't a licensed psychiatrist, so you have no place diagnosing him with some sort of work-himself-to-death mental illness.

The most likely and simplest explanation is that he believed he needed this job in order to survive, and as the staff around his job function was reduced and he was given more to do, he felt he had no choice but to do the extra work that was assigned to him, or else lose his job and suffer financial ruin.