I think it's simpler,money has no Color, no religion.
Silicon valley just happened to reside next to the hippies in the first decades
Now it goes beyond money: they are aiming at shaping societies. From mars colonies (imagine musks tantrums when they vote him out) to project 2025 type of political works.
When you have too much money, it's kinda boring to keep making more of them. You want self-expression to the max extent the society will allow you.
So why would it take off there instead of in a larger city with more resources?
I'm not disagreeing with you completely, but I would like to know more about what other factors you would consider to have been more impactful. I don't know that you really need hippies around to get that kind of 'california capitalist' mentality either tbf.