Cult Favorite Cartoons + Social Media Addiction = Acting Stupid For A Few Minutes Of Fame. Nothing new in that, the wildcard here is the McDonalds factor: the only participant that isn't actually as stupid as they seem.
McDonalds has always been crazy like a fox: staging shortages and pretending to have "no idea" how popular a novelty item is when they inexplicably remove it from their menu. Because, you know, the biggest fast food corporation in the world, the one that invented the efficient business plan everyone else follows, is completely clueless and stupid about consumer demand and its supply chain.
Nah, they know exactly what they're doing. The first time it happened, maybe they really were surprised by the reaction to their McRib debacle. But they learn fast, quickly figuring how to monetize "mistakes" and milk them for publicity. Ten years ago it was via TV coverage, it appears they're getting more savvy about social media triggers.
Remember the "Minion" toys they gave out in Happy Meals that shouted "Fuck You" to kids? That was my favorite.