In a chapter of this book, Robert T. Kiyosaki is going against diversification, which is a financial advice praised by almost everyone. In his mind, diversification will kill your returns as you'll spreading yourself too thin.

Instead, if you really know what you're doing, then you should invest heavily in it. In this case, diversification will slow you down instead of pushing you forward.

So, a person who has a deficit in vitamin C for example, will just go and buy a Vitamin C supplement. That's where they'll have the best return on investment.

If that person didn't spend enough time to understand where the deficit is coming from, and went with the diversification road, they'll end up getting a multivitamin and probably no return from it.