The problem is not 100% supply. Supply is just sub-component. In this case Oakland had been zoned for many of those buildings for decades now (Jerry Brown had a 10,000 homes plan). I'm moving in to a building that was entitled in 2007 but didn't open until a few months back... Locally developers couldn't get projects to pencil out. After SF hiked a bunch of rates Oakland suddenly became financially viable for them.

There are also the issues of tenant protections (most of the unsheltered people in Oakland lived here better living on the streets, and they still have jobs here) and making sure low-income affordable housing is built.