An idiot with capital will, relatively quickly, lose all of his capital through wasteful spending. You see this all the time with lottery jackpot winners, those who receive a large inheritance, etc.
The point is one might luck into getting rich. Staying rich requires some intelligence, or you're going to make poor decisions. This is even true of dynastic wealth.
Not so. The reality is that his family banker will invest the money in an index fund like S&P500 for him and then he will see it compound a predictable 10% or so every year, becoming increasingly wealthy without ever having to lift a finger or exercise a single neuron.
More likely the banker will invest it in low performing actively managed mutual funds and slowly drain 1-2% in additional "management fees" out of him...
In this society, a complete idiot with capital can achieve much more than a genius can achieve without capital.