I personally think that the issue is orthogonal, but correlated.
Liberal policies in the US are highly correlated with high population density. Even in red states, the cities are mostly outposts of blue politics; even in California, the rural landscapes are dominated by red politics.
Communities seem a bit like ponzi schemes, or are at least creatures of inertia. If the community is growing, it exudes promise and hope and more people are interested in moving there. Growth leads to job openings, which leads to more growth. The inverse is dire. When cities go bankrupt or when rural areas lose residents faster than they replenish them, it becomes a downward spiral and a self-fulfilling prophecy.
Rural areas don't sustain themselves. Urban or "hip" suburban areas have a much better chance at sustaining. College towns constantly have fresh blood (so long as the college stays out of bankruptcy).
I think cities thrive despite the friction created by more socially liberal policies and higher taxation. It's far easier to pivot your business and there are more serendipitous events in densely populated areas with highly educated people. I suspect people would prefer to move to a place with a reasonable social safety net as religious institutions lose the prestige they once had in the US. Perhaps in liberal areas people don't have to fear the social darwinism of the similar situation in a state+county with no funds to help the poor/homeless.
The obvious counter-example to "liberal policy places thrive" is Detroit. Detroit had very liberal policies in a state with very strong labor laws. After car manufacturers moved their manufacturing to cheaper labor areas (the US south and other countries), Detroit's population collapsed to less than 50% of it's peak.