OK that's one thing, but still there are many new billionaires that didn't exist a few decades ago, let alone a few years ago. Why did they become billionaires and the wealth didn't distribute over a much larger group?
Is the rate of billionaire generation increasing? Maybe that is the distribution in practice.
Wealth doesn't go straight up, it bubbles up.
And thinking about bubbles, imagine what happens when the GenAI one pops. The wealth some new billionaires had will go up in smoke, their assets will go on sale, and they'll be gobbled up by the old billionaires.