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.

20% of the population is already rich and wants to pull the ladder up after them.

That 80/20 split is about the same as the have/have-not income split of $160k/year.

20% of people know there isn't anything that govt can't make worse

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.