With all the barriers involved, its amazing affordable housing gets built at any price.
Hold a referendum to elect the constitution. Assuming it passes, you select a commission of people in charge of it. They get absolute power over anything relating to property - eminent domain, changing zoning laws, and giving building code exemptions.
It would only work if there's a democratic majority in favor of it, but if it did, what would be the issue? Then it would be very simple: just buy up some land, start building, and rezone anyone who complains as heavy industry and evict them.
I'm of course writing this in jest - hopefully they wouldn't have to be that draconian - but why hasn't anyone tried this? Is there not an electoral majority?
Because the electoral majority is a part of, or gets kickbacks from, the massive amount of bureaucracy! The vast majority of voters own property, and having a constrained supply benefits them, so barring a massive economic crash that wipes out most their property values.
Why would they ever change their ways? Clearly, people are still dying to move there, because that's why the prices are so high in the first place- so unless California became the next Detroit (and there are no signs of that so far) they're going to continue.