California NIMBYs generally consider themselves to be saving the world from overpopulation. That’s mainly an object permanence problem, but it’s true that high housing prices deter household & family formation.
There’s also the old canard about how environmentalism demands maximally convenient driving and parking because congestion and hunting for spaces causes cars to run longer.
My parents are from the "boomer" generation, and their idea of environmentalism is pretty good in a lot of ways, but in terms of lifestyle, they think of it as "live on a big lot with a lot of trees and drive everywhere". Yes, they get to see lots of green - but they are very fossil fuel dependent.
There really is a shift in mentality from thinking about what you see out your front door to thinking about the whole thing as a global system, and not everyone is capable of connecting the dots.
Supposedly protecting the rare endangered birds keeping high density housing from being built next to mansions on the Malibu shore is extremely environmentally friendly NIMBY.