Looks like it's all about inventory. No one is selling their home in Santa Clara County (San Jose)[0]:
Homes for sale in March 2016: 1,254
Homes for sale in March 2017: 934
Homes for sale in March 2018: 516
Homes for sale in March 2016: 1,254
Homes for sale in March 2017: 934
Homes for sale in March 2018: 516