The person, our group of people, who have built the specific heap of wealth (e.g. a company) are the best stewards in my opinion. It does not mean that they WILL increase the wealth even more, they might run it into the ground, but they are the only ones who have the moral right and probably the experience.
Then consumption isn't the dispute, and the yachts are a distraction. So the question is what unbounded accumulation buys that bounded accumulation can't. Not welfare, since you've just said it's all reinvested.
What's left is control: over which projects get capital, which technologies get built, which politicians get funded. $250M toward an election is the same capital, doing the same "allocation." Is concentrated control over allocation a good we should maximize? And is "they built this heap" a sufficient moral title to it, including when the heap was inherited rather than built (which is the majority of the time)?
Without that you will always run into these sort of issues. The problem isn't wealth inequality, the problem is that wealth buys political power.