The difference between average "stupid" and average "smart" is nowhere near significant enough to make a practical difference. It's a question of how willing someone is to take advantage of their situation.
By maybe 3 years old, humans figure out they can lie about their ignorance of what's generally good or bad to get away with a ton and that will be taken advantage of until some sense of accountability and honor is learned, or there's some significant threat to their personal well-being. A lot of people don't get past that stage until their late teens, but young people don't have much opportunity to do a ton damage with that mindset, they don't tend to have much power. Some people never develop the sense of accountability and go on to test the limits of their feigned ignorance until they find the lines, and walk them as close as possible. As adults, on average, they may not "succeed" as much as "smart" people, but the problem is, people like that are more likely to seek a position that allow them to get away with it, and "smart" people keep letting them off with a look of disappointment, and the assumption that they've "learned from their mistake" and won't do it again, but what they've really learned is they're not as close to the lines as they thought and go a little further next time.
