This figure from a Wired article is pretty wild
In 2006, companies in the Bay Area brought in 21 percent of all venture capital invested in tech in the US. By 2016, that figure had risen to 35 percent.
by way of contrast, other cities are pulling in far, far less. Denver, for example, less than 1%.
That is a big issue, and not just because of the availability of high-risk capital. As you read the above article, the main problem is finding the connections that you need to move an idea into a minimum viable product. That takes some money, and it takes designers, programmers, etc. An ecology that is oriented around high risk/high growth projects.