One reason is that Valley Fair is the closest there is in the Bay Area to a good East Asian mall. For example, their recent expansion brought in a good variety of restaurants, particularly Asian restaurants, that attract the wealthier Asian residents of Silicon Valley (plus Whites, who in the Bay Area are pretty Asian in habits). These bring in a crowd of regular visitors that will stick around to occasionally shop at the expensive stores, even if they don't love conspicuous consumption enough to buy there all the time. Also a decent number of more youth-focused stores that draw in all demographics - after all, everyone in the younger generations loves anime and K-pop.