I pointed at my kids and said "They happened. And they take all my time."
I was a full-time wife and mom. This is not a career known to lead to great wealth.
So, for starters, not all interests or career paths have equal potential to lead to wealth. Intelligence in no way guarantees that your interests will happen to nicely line up with things that lead to wealth.
Everything I've read suggests that being born into the right family plays a huge role in wealth, a la the joke "He made his money the old fashioned way: He inherited it."
Health issues are another thing. Miracles of modern medicine can be very expensive and come directly out of your pocket if you live in the wrong country. At the same time, you typically will be less productive and less competent while enduring serious health issues.
Personal relationships are another biggie. My mother used to work for an heiress whose husband ran through her money. After the divorce, she had to get a job to support herself.
Divorce, scandal, drug addiction and various other personal issues can all be financially ruinous.
Even if you are good at earning it, that doesn't mean you are good at keeping it or growing it, a la some tagline from some magazine "How money becomes wealth."