There are a couple of nuanced issues with what you are saying.
1. In our current political system, wealth translates into political power, which can (and is) used to change laws to secure more wealth - just look at the portfolio performance of members of US Congress. Democracy is about putting political power in the vote.
2. Many if not most of our important problems are beyond the ability of one person (or a small group) to tackle - climate change, food security, etc. Having wealth more distributed means that more economic participants are involved in deploying it, and thus greater predictive power per dollar spent.
1. In our current political system, wealth translates into political power, which can (and is) used to change laws to secure more wealth - just look at the portfolio performance of members of US Congress. Democracy is about putting political power in the vote.
2. Many if not most of our important problems are beyond the ability of one person (or a small group) to tackle - climate change, food security, etc. Having wealth more distributed means that more economic participants are involved in deploying it, and thus greater predictive power per dollar spent.