It is actually sort of surprising to me that cities are tech hubs - you should be able to deliver fantastic products while working remotely and never meeting anyone in person. (And the free software/open source movement is an existence proof of that.) So there must be something else about cities that makes them better at not just the success of tech companies but the success of groups of tech companies.
Left-wing policies like urban exclusionary zoning? Yeah right. Look at how Texas and other Sunbelt states are doing, despite them being in inherently more challenging parts of the country than CA.