Yes, the reason those people support Democrats is that they are educated and live on the coast. Tell me where you live and what your level of education is and I am happy to place a very large bet on your political choices.
So you're admitting that basically this entire sector of the economy is a monoculture, but downplaying that there's any negative systemic bias cause that's somehow just a deterministic function of geography.
I am stating as a simple fact that education leads to a tendency to have a particular political affiliation given the current stances of the two major parties. This has nothing to do with a particular economic sector: college-educated truck drivers and college-educated lumberjacks would be the same. Reality has a well-known liberal bias so it turns out that this education-influenced tendency is more of a positive systemic bias than a negative one.
> education-influenced tendency is more of a positive systemic bias than a negative one
If anything, there's evidence that education has a negative influence in ways you may not expect. I seem to recall Germany being the birthplace of the modern university, "Humboldt's Ideal," and we all know how they ended up. In fact, doctors in Germany were 7x more likely than the average citizen to join the Nazi party. [1]
And the issue is more about disposition, the educated seem to have an extreme blind-spot because, as your argument evidences, they tend to think so highly of themselves. They also have the mental machinery capable of producing very enticing & sophisticated, but ultimately wrong justifications for horrible things. And in combination with a self-righteous moral self-concept, you're playing with some real fire.
Read C.S. Lewis's God in the Dock, I'll quote:
"Of all tyrannies, a tyranny exercised for the good of its victims may be the most oppressive. It may be better to live under robber barons than under omnipotent moral busybodies. The robber baron’s cruelty may sometimes sleep, his cupidity may at some point be satiated; but those who torment us for our own good will torment us without end for they do so with the approval of their own conscience."
Maybe it's useful to point out what you're not saying: That there is any sort of virtue in being "educated" (whatever that means).
Perhaps more to your point, most state run institutions seem to also lean left. This effectively turns your argument to "Educated people think like us and therefore we can trust them with the right choice for us."