I gotta wonder if meme-humor is what is left when postmodernism finishes the generational, Nietzschean work of killing God. No, seriously. Nietzsche originally started out railing against pietism, and a core element of that was encoded art - artwork built around shared cultural, ideological cues. A lot of classical art is mildly opaque to a modern audience, and it has to be explained because all of the biblical, allegorical, or pagan references assume a belief and education context which isn't present in the viewing audience.
When did "art appreciation" become a goal of education? Sometime in Victorian times? Dimitri Rotov used to go off on rants about the kitschy folk-music krep which reinactors and documentarians like to use to "signify" the ACW period; he insisted that the soldiers of the Army of the Potomac were highly cultured, and fond of highbrow opera music as a matter of course. It wasn't opaque, it wasn't difficult, it was popular culture, because everybody shared the right set of references, mostly religious.
The early Twentieth Century, all those religious references fell out of high-culture favor in the west, and were replaced by first Marxist, then Freudian signifiers. Those both burned out by the Seventies, although Freudian lasted longer in culture than Marxism, far as I can tell.
But people want and need signifiers, meta-content. To a certain extent, it's a need for meaning, no matter how nonsensical. Once you as a culture accept absurdity, madness becomes your meaning. Thus, Mario in a stained glass window.
[Deleted and re-posted after I discovered the purpose of that "harmless" comment spam - I'm pretty sure now that it's a marker for spambots to discover active blog comment sections. Pests.]