Short answer: early Silicon Valley needed space for fabricators, the dotcom era needed space for data centers, then around 2010ish there were enough cloud provi

Short answer: early Silicon Valley needed space for fabricators, the dotcom era needed space for data centers, then around 2010ish there were enough cloud providers and internet connections you could start a company anywhere but you already had plenty of talent in the bay and San Francisco is fun. Long answer could be a phd thesis but “people needed lots of space until they didnt” kind of suffices.