Mainly current homeowners. A constrained supply almost guarantees that your home value will continue to go up, especially if you're in a lucrative area. So homeowners and well-connected people make sure that zoning laws and building regulations are very prohibitive to new construction housing.
I guess it's easier for local politicians to get poor people angry at "evil foreign tech giants" instead of actually solving the issue. That way they get to cash-in on votes from both groups!