There are two ways people measure wealth: absolute and relative. You can also score it individually or societally.
If rich people are trying to maximize absolute societal wealth, you'd be right.
However, if they're trying to maximize absolute individual wealth, then they have plenty of incentive to exploit people. Labor history is full of this. If my workers aren't my customers and the choice is between putting a dollar in my pocket or a dollar in theirs, then a wealth-maximizer is going to take the dollar every time. Does that mean less global wealth? Very often. Does an individual absolute wealth maximizer care? Not at all.
People, though, are primates. Dominance hierarchies are part of our evolutionary history. We don't just care about absolute wealth. We care about social status. For many, power is its own end. Power and its signifiers. E.g., positional goods are hugely appealing to some people. (As a great historical example, consider the Shakespeare-style lace ruff collar. It was the height of fashion when it was handmade. As soon as machine-made lace became possible, they went out of fashion because they no longer reliably indicated wealth.) For these people, what matters is individual relative wealth.
For some people, yes, the exact desired outcome is them being on top and everybody else well down below. Does that mean they are less absolutely wealthy? Sure. Do they care? No. For evidence, just look at the historically enormous number of kings, dukes, warlords, etc, etc. Most of the world for most of history has been run with approaches that are miles off "greatest (economic) good for the greatest number". Conspiracy is entirely unnecessary to explain that, just individuals seeking social dominance by any means that come to hand.