Other than Stanford, I don't think that SV really has educational institutions as its driving force.
My opinion is that there are 3 main drivers and that top tier education is one of the most important ones.
They go like this:
Higher education that has enough gravity to aggregates diverse 'cutting edge' people from a variety of pursuits.
A reason for those smart people to stay that isn't just money. I think that's lifestyle and access to nature. You have the ocean, mountains, wine country, and relatively good weather.
The last is capital, I think saying companies is putting the cart before the horse. When I say capital I don't just mean startup capital. The ecosystem has to also have liquidity. There are lots of areas that have one of the 3, but very few that have all of them.