An oligarchy isn’t defined by a set of stable oligarchs. There can be a shift in power in a oligarchy and there typically will be because the oligarchs aren’t friends.
If you look to ancient Athens, it wasn’t uncommon for an oligarch to be exiled. If you look to modern Russia, well, there is a reason a lot of former Russian oligarchs chose to live in London and not a Russian prison.
An oligarchy is almost always a turbulent place, most of them making the BTC powershifts look calm.
Churn at the top is the exact thing you want in a dynamic, robust economy. You don't want equality. You want movement. Sure, Russia and Athens had some churn. But it was incredibly low.
It's still a small group in control, so still an oligarchy. But the fact that there is a constant rotation of oligarchs makes it a little different, like maybe you could be the next oligarch.
