Factors!
From what I've read 20%+ of the buyers in CA are cash-rich Chinese buyers. If they blow $500k+ on a house, stay there 3 years, they become U.S. citizens. Same thing is happening in Miami with Latin Americans doing likewise.
Take out the Chinese buyers, and?
Then there's the extremely selfish, powerful, anti-density NIMBY's. Just an example: a developer wanted to build an iconic 21 story condo building in Santa Monica a couple years ago, designed by Frank Gehry, it would have been the first high rise in Santa Monica since 1970! And what became of that proposal?
The powerful California Coastal Commission will never allow Miami area high rises along their shorelines, not even mid rises. And who is on the board of the Commission? Single family owners with homes along the coast?
A developer wanted to build an urban Manhattan high rise village in Hollywood. Last I heard: this proposal will first have to go through several neighborhood committees before it's approved. And how long will that take? A decade? And wait until it reaches the Nimby's in the Hollywood Hills, where this project might block their views of the smog or the Airport!
San Fran-Nimby is hopeless, largely ruled by the Nimby Kings and Queens of the Hills. How dare they even propose a mid rise or high rise that will block their views of the Bay or Alcatraz!!! Yes, there's some high rises going up in the Mission District, but that's OK, because that helps block their views of Oakland!
And across the Bay, Oakland/Berkeley, you've got a very high percentage of anti-development, anti-density Nimby's as well.
There's a method to their selfishness. Sell their over-priced homes in their retirement years, and with that big chunk of money, they can buy 2 or 3 retirement houses.
1 out of 3 move here to Las Vegas. I've met a number of them. Sold their overpriced homes, bought a house here for a third or 4th of the price in CA, and they sock the rest of it in the bank, yup, retire at 50!