With human benevolent dictators it doesn't work for long. The weak point is that particular human. Which is an argument for why what any particular "billionaire" says today is irrelevant.

Their promises mean nothing, what matters is the game strategy and the equilibrium. Not what they promise to do, or not do.

So, with a hypothetical entity that knows best than any human, or any group of humans, it's hard to argue for human control. Because the humans who have control want it for a few quite particular reasons, and it rarely has to do with the benefit of everyone else.

There is no such thing as a benevolent dictator. It is a contradiction in terms.