‘Oligarch’ doesn’t mean ‘rich dude’ - an oligarch is by definition someone (a member of a small elite group) who exercises control over a state.
The point of op wasn’t that Bitcoin transfers power from states to existing oligarchs - indeed, that would be nonsensical, as by definition oligarchs already control states - but that it would transfer power from democratic state institutions to oligarchies. Ie it would create new oligarchies and supplant democracy.
Isn't having more power brokers healthier for a democracy than fewer? Today, the existing oligarchs control both the currency and all the laws. This at least fragments that further. The existing oligarchs still get the government; that doesn't change. The new ones get the currency.
The point of op wasn’t that Bitcoin transfers power from states to existing oligarchs - indeed, that would be nonsensical, as by definition oligarchs already control states - but that it would transfer power from democratic state institutions to oligarchies. Ie it would create new oligarchies and supplant democracy.