SpaceX has pursued the permit for some time after first identifying and subsequently leasing the site back in 2018. As notes, the company has the option to terminate the permit within 180 days, and indeed, it canceled a similar permit two years ago when it moved the initial phase of the Starship project to Texas. However, the Los Angeles Port site brings Starship development closer to SpaceX's headquarters in LA, and written into the permit contract is the option to expand the site from 12.5 acres to 19 acres, so it seems SpaceX is committed to the location.
Councilman Joe Buscaino, whose district includes the port, said, "It's crazy that here we are in 2020 preparing ourselves to send people to Mars, and it's going to happen in our backyard. We are becoming a spaceport." There won't be any launches taking place at the site, however -- the facility will be used only for research, design and the creation of components. According to Musk, the Starship will be ready for its first test flight later on this year.