They’re the constituency that supports Trump.
Numbers like GDP or total wealth will be highly misleading — and it’s unsurprising that the opinion of the petite bourgeoisie (who primarily make up HN) differ from those groups.
There's no dispute that America has become incredibly more rich and powerful over the past 40 years. The fact that that money is increasingly funneled to fewer and fewer people (as a percent of the population) is something that can be changed locally, without changing our foreign policy stance.
It's not a surprise that the "devastation" of the middle class coincides with the continued reduction of tax rates on the entities collecting all that money. The America that MAGA seems to think was great was one of higher taxes and more social programs.
The manner in which those people accrued wealth is deeply related to the issue, by subverting the working and middle classes domestically.
I understand that many of the petite bourgeoisie believe that destruction of those classes via internationalism is a means to usher in communist policy — but that’s opposed wholesale by the American working and middle classes.
You're still describing economic policies though, not diplomatic ones, and while they're not entirely disconnected, trying to fix international economic issues by burning down alliances is likely to result in a lot of negative second order effects while not even addressing the main economic concerns.
If we're ascribing bad faith motivations to particular viewpoints here though, I'll point out that conflating concerns about trade policies with the idea that America should entirely abandon any interest in the rest of the world is enormously helpful to countries that would like to pursue far more aggressive imperial ambitions currently being blocked by American power. Having rightfully angry people in America's rust belt become convinced that the only way to revitalize the industries that used to power their cities is to let Russia reform the Soviet Union has got to feel like the political victory of the century to Moscow.
When the party advocating wealth redistribution also calls them “deplorables” and flagrantly provides worse services (eg, NC disaster vs CA disaster) that seems like a reasonable belief.