In the late 90's until the tech collapse, many "investors" who had little to no experience or knowledge made out-sized returns "day trading". Some even quit their jobs because they thought they were good at it and had the profits to prove it. Then the correction hit. I haven't seen/heard of so many people thinking that they know more than the market since then. They will be punished. Question of when not if.
Yup, my brother was one of those people. He was convinced that he was a genius. Until he wasn't.