1. Being in extremely left-wing Bay area with historic ties to the free speech movement. 2. They're not, it just benefits both the tech companies and the media to portray them that way.
Add in the visa/immigration issues. A large percentage of the workforce in SV is imported from outside the country. While the business wing of the Republican Party loves cheap labor, there are other wings that oppose it. Once upon a time the labor wing of the Democratic Party would have been against importing labor but the influence of that wing has waned considerably while the business wing has established itself in both major parties. If you're not a native born US citizen, a label that describes quite a few tech workers in the Valley, the left seems more aligned with your continued existence in the United States.
> "A large percentage of the workforce in SV is imported from outside the country."
Imported mostly from East and South Asia, from very socially conservative cultures. I wouldn't be so quick to assume that they're necessarily aligned with the Democrats.
They mostly are, although this is a recent phenomenon. Growing up in the 1990s, Indians/etc. in my area we heavily republican, consistent with their higher income levels and general social conservatism. In the 1996 election Asians went for Dole by a slightly larger margin than white people. But today, Asians vote Democrat at a higher rate than Hispanics.
Worth noting that the difference between neoliberal and left-wing wasn't really brought into focus until a few years ago. Also worth noting that Pelosi advocated for single-payer in the 90s then made a rightward turn.