There was a progressive/conservative switcheroo back in the 1920’s.

Eh. There was a rapid decay of progressivism in the Whig-turned-Republican Party in the 1880s, culminating in several decades of fascism, oligarchy, and outright White Supremacy as the prevailing order of the federal and state governments. This peaked with Coolidge in the 1920s and have birth to a brief US flirtation with Communism as an active movement.

Republicans used to be the progressive ones. The Whigs predated that.

Plenty of Whigs were progressive. Conscience Whigs were a political force across New England long before Republicans existed as a party. And they were the first to defect en mass to the Republicans when they did manifest.

Infact some of the more “bought” examples spun off and formed what became known as the “Do Nothing” party because they were so waffly on the issues and fond of status quo milquetoast non-positioning

Do you mean the "Know Nothing" Party? Because that was a secret society which operated in direct conflict with Conscience Whigs, effectively splitting the organization in 1854 and giving Republicans an opportunity to emerge onto the national scene.

I thought they were the "Know Nothing" party