I have a theory, completely invented in my head: In various places, “everyone understood the assignment” became a sort of memeish way to describe videos and gifs in which a bunch of people spontaneously work together to accomplish something cool. The first time I saw it was at the link below. I think someone was riffing on that, and then it sorta went viral and is morphing before our eyes from there. https://www.reddit.com/r/PublicFreakout/s/uBwpaE4jcU