You really can't make that claim unless you had the chance to see their IQ scores first hand. Some genius aren't so obvious. Some of them like to have a "dumb" down outward appearance.You do NOT have to be a genius to be making money in trading. LOL Warren Buffet, George Soros, Jesse Livermore, all successful traders but I do not consider them geniuses. Steve Hawkins, John Nash, these are geniuses but they don't trade. So it just shows that you have to be in a different framework of mind when it comes to trading.
It's not that they are trying to be humble. But "dumbing" down can be a distress/relaxation mechanism to slow an "overactive" brain down. Me personally, I prefer using alcohol. Hehe.