Concentrating wealth to the degree of the US is not at all necessary for innovation. As an extreme example, Bezos would have done the same thing for a tenth or less of the current lifetime income.

In fact, when many leading entrepeneurs started, the wealth concentration wasn't nearly as high, yet they were still motivated. Now with wealth concentration much higher, my impression is less motivation and opportunity for startups, innovation, starting a business in your garage, etc. In more economic terms, I think it's well-established that such high concentration of wealth reduces economic mobility.