I believe that the fight is more by developers than residents. It's a zoning outcome, after all, and most people, I suspect, don't keep on top of that being too busy with the lives
Maybe you are right. I live in the bay area and people here who lucked out buying a house in a normal time at a normal value have nothing to do but show up at all sorts of public hearings, meetings, etc. and shout down any kind of new development
More supply can reduce the value of that asset, so people fight it, especially if they have financially planned for that asset to appreciate over time