That sounds plausible. There was one teacher I had who seemed to have a complete personality change after he nearly died (heart problem I'm pretty certain). He went from being demon* who specialised in humiliating students to being pleasant and easy-going.
The first time I ever interacted with him was in front of the public when I did my very first bit of what might be termed work experience when he loudly proclaimed to all around that he was dealing with the "absolute pits here"
Yeah, a guy I worked with was known for crazy outbursts as well. Really mean behaviour, that sort of thing. After he got married and had a kid it mellowed a lot. And that's despite his frustrations with work being the same.
