I never watched their reality show, but from the clips I assumed it was drugs, or the aftermath.
Arlo’s mother Marjorie split from Woody. I think that was when everyone thought Woody’s problem was drinking. He remarried for a year, and then he got the diagnosis. If I remember properly, Marjorie took him in, and then spent plenty of time with him once he was in the hospital. That was about ten years. Yes, it was for the children’s sake, but the biographies portray it as more.
I think one of Richard Pryor’s wives got cared about him after he got ill.