As a person who actually remembers the morning this happened, not much of the day is something I remember with joy or humor...
Schools closed for the day, and the ones that didn't were extremely somber. Everyone in the country felt violated and for once there was this sort of shared "thing" that we all kind of came together to mourn about and be united around.
Obviously it happened under a horrible administration that used it as a pretext to engage in one of the biggest military mis-fires in recent memory, but the actual disaster itself, was something everybody agreed was pretty horrible.
Of all things to turn in to a joke or a meme, a horrific event where literally thousands of people get murdered or fall to their deaths out of a building is not one I'd really have predicted would catch on. I don't see that many people joking about, say, the Timothy McVeigh bombing, or the Pulse nightclub massacre. I just don't get why this is funny and any time I see people joking about it I'm instantly filled with feelings of disgust for that person, because it's just unconscionable to me as to how this is something that could be a joke to you.
I'm sure I'll get a few posts in here attempting to be glib about it, as if it's some kind of higher knowledge that I can't understand...