That is an utter fallacy.
Stupid can and DO become rich.
Wealth does not equate to brains.
Really?
Think about all of the qualities it takes to become rich. You have to have a product or service to sell, and know how to sell it. You have to network--this is how you find the people who can do things for you. You have to know how to manage your money, or find someone to manage it for you. As you become even more rich, you have to know how to find competent managers. I could go on, but the bottom line is that stupid people do not become rich.
Don't be fooled by the public persona Kim Kardashian puts up. It's all part of her business model.
If you seriously think that it does not take a ton of savvy to become rich, consider what happens to many lottery winners. They lose the money. For the most part, these would be people of average intelligence. But they don't have the skills or intellect to be rich--even when they get a head start through winning a lottery.