It comes down to the notion that America is a classless society being farcical. There has always been an elite that jealously guards their power and influence. Entrance into it - or the ersatz version that is the bourgeoisie - has always (along with immigration) been modulated based on what was most likely to preserve the existence of that elite.

And it's not a conspiracy; it just shows how much power that elite has, that they're able to make these things happen when they need them to. A sudden turn away from nativism and condoning of proto-anarchy when the black population (first slave, then free) threatened to upend the social order. Socialism lite (and more immigration, but only from preferred European nations) to head off full-blown socialism after capitalism first drove to excess and then blew itself up. Truman getting the VP spot. Bank bailouts (so many bank bailouts). Even the begrudging "opening" of elite institutions to Jews, blacks, Asians (staring down the barrel of their own, rival, institutions).

Anything to prevent their power and influence decentralizing in an enduring manner.