That graph is what the herd behavior looks like. But if you break down, take 2 people who are actually on bottom quartile. While on average they think they’re 3rd quartile aka a bit above average, one of them will have impostor syndrome and the other one will think they’re the smartest person around. Then for the top 2 smartest people around, one will know it for sure and the other will think of themselves less than the overconfident newbie described above.
water coolant in nuclear reactor enters the chat
Marketing person looking for fancy drinking water enters the chat
Narrator: you wouldn’t guess what happens next
<Insert Pikachu meme>