This is not true. There is a history of technology entrepreneurship in Silicon Valley going back (at least) 60 years. There are a great many pieces of human infrastructure that exist in SF that do not exist in Portland from the largest collection of technology VCs & Angels in the world, to lawyers that understand corporate structure and stock options, to bankers that understand IPOs, and of course thousands and thousands of engineers.

A 20 year difference if a vast understatement.

The Bay Area had many large defense contractors employing a lot of engineers. I don't think that should be underestimated.