It’s true that he might have been motivated by money as much or more than by the attention. There are good arguments on both sides, but the majority opinion seems to be that he’s the first example of MbP/FDIA in a man that we know of. I think that money should be considered an acceptable co-motive for a diagnosis of FDIA, because so many perps use their children’s illness and deaths as a way to scam people for money *and* attention — Dee Dee Blanchard is a perfect example.
As for the substance abuse, I really don’t know. Since he was transferred there after he had already been serving his time in “regular” prison, I have to assume he got addicted to something while in prison. Unless we can get a cellmate to talk, we’ll probably never know what it was, since it’s covered by HIPAA.