The oligarchy already isn't really people. Yeah, your billionaires might be the public face, but the true form of the oligarchy is institutions. Which are not that far from AIs already. ChatGPT (for example) leverages human intelligence by extrapolating trends in human produced texts. Goldman Sachs (for example) leverages human intelligence by employing humans to perform tasks for it.

Institutional Intelligence already has little compunction to align its goals with human wellbeing. Pair it with machine intelligence and what happens? Do we just get a more efficient version of our current mess? Or do they take human will out of the loop entirely?