I would guess the NIMBYs "somewhat support" affordable housing (i.e. "somewhere else, just not here"), and that they're mixed in with further home owners who are afraid of lower prices affecting their "investment." I imagine it's mostly real estate speculators that make up the bulk of the ones against affordable housing.
Actually, the government directing the CHMC to pivot from "direct public housing investment and urban planning" to "mortgage supports and bribing developers" is about the same time our housing market started to get out of control.
I don't think this is quite true. I think there's a lack of understanding that affordable housing has historically been a public infrastructure project until we stopped doing it. Anecdotally I know plenty of people who understand affordable housing as welfare that can't solve the problem, instead of a non-market solution to a problem that the market can't solve, similar to healthcare. Those are people who understand why healthcare is publicly provided and support it.