"Successful" is the key. A winning lottery ticket is one of the quickest ways to get money, the hard part is the "winning". If you are smart, there are many career paths that are highly likely to be very profitable, with small risk of failure and a pretty high floor. That is not the case for starting a business. The upside is potentially much higher, but it is much less likely, and the downside is huge.
Having access to capital is much more important than smarts, which is why so many people starting businesses have generational money propping them up, or as a safety net. Even smart people are usually reliant on that family capital. Bill Gates’ parents were millionaires, Musk and his dad’s emerald mine, Thiel started his first hedge fund with a million dollars raised from “friends and family”.