Whilst it is crystal clear why wealthy individuals and large corporations are against such social progress, it has often been a source of confusion why many lower income individuals seem to vote against their own interests by refusing to support measures that would objectively improve their own lives.

This is -backwards. The rich are for social progress, because public peace is all they need for the quiet enjoyment of their wealth. Businesses are for income equality because that's where customers come from. There are game-theoretical reasons why individual businesses cannot just raise wages or lower prices, but ever since Henry Ford started making cars his workers could afford, savvy businesses have negotiated working arrangements that boost demand for their products in a macro way. (Some business owners are stupid. It's their stupidity, not the mechanics of capitalism, that drives their action.)

OTOH, the lower middle class has the most to lose from equality. Those immigrants and ethnics represent additional supply of the thing (labor) these people have to sell. OF COURSE, they don't want newcomers. Delusions of mobility do not drive working class voters. Exactly the opposite is true. They expect not to advance, and so are very fearful of falling backward.

Capitalism is the best thing that ever happened to salt-of-the-earth humans. Did serfdom improve as rapidly as the condition of labor under capitalism? Globalization has been bad for laborers in rich countries, but that's because we lack the political tools to coordinate the advancement of labor's interests across sovereign borders. That's where attention should be focused. (FWIW, I prefer boycotts to international government.) Reducing trade with places the screw workers should be a high priority for labor advocates in rich countries. Labor should be trying to make the world safe for capitalism to continue to create prosperity for workers

The supply chain issues raised by COVID - it's an ill wind that blows no one good - and the German dependence on Russian gas have shown us that globalization has a nasty downside independent of its effect on workers' standard of living. Those problems may provide some political cover for the more important economic goal of making "labor" an illegitimate source of comparative advantage.