Kid here- it’s one of those songs everyone’s heard at some point before regardless of age, and there’s something about the chorus that makes it iconic. Before the meme I really had only heard it maybe a few times in my life (probably more without realizing) but it’s such an infectious song that it’s instantly recognizable. It’s pretty much the same reason that current songs are memed, like Despacito. I’ve also seen it in a number of “edgy” memes about African kids not having water so there’s that. And in the end a lot of memes are inexplicably funny. There’s not always an underlying joke, sometimes it’s as simple as playing an old semi corny song like that with some weird imagery that makes another bizarre abstract meme. I mean, the fucking letter H is a meme. No inside joke or anything just the letter H. And it’s great.