That's simply not true. SV was built in the 60's thru the 80's long before the H1-B visa program started in 1990.
Maybe the OP means the modern SV aka FAANG and that is not far from the truth or very hard to disprove. Things turned out the way they did for a lot of reasons and none of them can be really discounted.
A little too specific, if you change "H1-B visa" to "immigrants" its most definitely true.
Correct, I meant all immigrants, not just H1-B.
The biggest employers of H1-B workers have almost always been consulting companies, most of them located well outside the valley.
That claim is no way incompatible with Silicon Valley having a large, prosperous, and essential H1-B workforce.
The bay area doesn't vote Trump. This is a natural response to the voting mechanism. Only swing states get pandered to.