Gregory Ferenstein, in the course of arguing that super-rich donors are about equally split between Democrats and Republicans (although the Republicans donate more in absolute dollars), points 
out that the super rich in Silicon Valley are almost exclusively Democrats. Why?
I think the more likely explanation is that the nation’s new industrial titans are pro-government.
Google, Facebook, and most Internet titans are fueled by government projects: the Internet began in a defense department lab, public universities educate a skilled workforce and environmental policies benefit high tech green industries. The CEO of Uber, Travis Kalanick, is a fan of Obamacare, which helps his entrepreneurial drivers keep their health insurance as they transition between jobs.
In other words, the Democratic party is good for emerging industries and billionaires recognize it. Donald Trump is a candidate known to go after major figures in tech; a trend that may further the Democrats friendship with new industrial titans.
Perhaps more importantly, I’ve argued that the modern emerging workforce of Silicon Valley, urbanized professionals, and “gig economy” laborers all represent an entirely new political demographic redefining the Democratic party to be more about education, research and entrepreneurship, and less about regulations and labor unions.
There’s something to this, but I suspect culture has a lot more to do with it. Most of these folks have spent their lives marinating in social liberalism, and being situated in the Bay Area just adds to that. So they start out with a visceral loathing of conservative social policies that pushes them in the direction of the Democratic Party. From there, tribalism does most of the additional work: once you’ve chosen a team, you tend to adopt all of the team’s views.
Beyond that, yes, I imagine that tech zillionaires are more than normally aware of how much they rely on government: for basic research, for standards setting, for regulation that protects them from getting crushed by old-school dinosaurs, and so forth. And let’s be honest: most of the really rich ones have their wealth tied up almost entirely in capital gains, which doesn’t get taxed much anyway. So endorsing candidates who happen to favor higher tax rates on ordinary income (which they probably won’t get anyway) doesn’t really cost them much.
For most folks in Silicon Valley, even the super rich, there’s very little personal cost to supporting Democrats. Combine that with an almost instinctive revulsion at both troglodyte Republican policies and the Fox News base of the party, and there just aren’t going to be many Republican supporters in this crowd.
