Then you don’t understand slavery deeply-enough:

They can outright remove-human-validity-from all lives except their-own, & they’ll still have “business” happening.

True, but a very limited one.
In a situation where you need to continually grow, removing all the human side of business will end with bankrupcy.

Citizens are not required outside of oligarchs…

Citizens are required, oligarchs can prosper only because there is something that produce their money. You remove the citizens, who in a form or another can buy oligarchs services/products, and the oligarchs are left with nothing, their money is useless.
We can discuss that then people will become money (the more slaves you have the better) but to keep slaves have a price, low as you want but it have it, and without a way of producing something you will end with no money and then no slaves.

Here we are talking about business that on one hand are trying to sell something to people and on the other are firing people to replace them with AI agents. We can replace, at the beginning, people who buy AI services with other business who then fires the people they hired to replace them with AI agents and so on.
At some point you will end with all the people fired (not that it could end this way in a pacifically), that cannot buy anything other then some food (if any) and a lot of business that are producing and trying to sell something to... who exactly ? The slaves ? Other business ?

Humankind’s history is waaay worse than you’re understanding.

Maybe, I never had the time to study history as much as I'd liked but I understand that there cannot be oligarchs without a society behind them.