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Although rich dad poor dad is a pile of worthless nonsense , you are correct to have come to the conclusion that building a business is the only way to build real wealth.
(If you haven't read The Millionaire Next Door, I would recommend reading that one...along with The Future for Investors, The Ten Roads to Riches, The First Billion Is the Hardest, & Buffett: The Making of an American Capitalist )
First a note about "millionaire." There are millionaires and there are millionaires. Since you wrote "multimillionaire" I will assume mean "rich" and not comfortably retired. Most millionaires in the US, whether or not they are actually retired, really fit into the later category. People like me who have worked hard, saved a lot, invested wisely (esp. in ourselves and in things we are really good at) and ignored much of the consumer world rushing around us (This is what The Millionaire Next Door is really about) It is possible to save and invest your way to a comfortable retirement. For people like me that will likely mean early retirement (55) and several million dollars in the bank, so to speak. I am not, however, rich in the way you seem to mean it.
To run things...to do what you want when you want to the way you want to is an entirely different thing. It takes enormous effort, tremendous risk, and a determination to do make your unique talents a profitable business. I have met more than a few of these people over the years -- including a few famous ones. They are intense and focused. Unlike the "comfortablely retired" they rarely do things the conventional way or slow down. They are not dreamers -- they are people who get things done.
No one has become wealthy and powerful without building an extraordinary business along the way. Even if they are seen as "investors," their real wealth lies in the businesses that stands behind them. Off the top of my head, see: Buffett, Soros, Pickens, Bloomberg, Peterson, Tisch, Kluge, Fisher, & Gross.