Neighborhoods fighting densification tooth and nail make housing scarce, and people who want housing having to outbid each other for (proportional to population) fewer and fewer houses makes them unreasonably, unsustainably expensive. Which attracts investors and adds icing to the problem, but at root it’s the homeowners who got theirs and then pulled up the ladder after driving the scarcity of housing in the locations where people want to live.

If people demanded governments really invest in densification and new houses where the jobs are - including sharply limiting the ability of noisy impacted neighbors to drag the process out - the availability of houses would force prices down, which would cause the predatory investors to lose interest and add icing in the other direction, to affordability.