Current U.S. leadership: Our billionaires are gonna be bigger than all the other billionaires in the world put together. (I honestly believe there's an insecurity motive there: if US billionaires don't amass significantly more wealth, they won't be competitive in the billionaire world against outside billionaires.)
U.S. Democracy: If one dollar = one vote, I guess we should save all that money we have been wasting on elections.
The real reason for the surge in prosperity of the middle and lower classes after WWII: decimation of the ultra-wealthy throughout the developed world. Remember: the post WWII US income tax on the wealthy was 91% - literal decimation, for those who paid.
https://www.wolterskluwer.com/en/expert-insights/whole-ball-of-tax-historical-income-tax-rates
I could see myself wanting to own multiple private islands, getting Larry Ellison to sell me Lanai is going to take a lot of money.