Oligarchy means controlled by the few. Anyone with a Raspberry PI, decent network bandwidth, and a few terabytes hard drive can be a node and start validating

Oligarchy means controlled by the few. Anyone with a Raspberry PI, decent network bandwidth, and a few terabytes hard drive can be a node and start validating and relaying transactions. Besides, Bitcoin is not proof of stake, so having a lot of bitcoin does not give someone more control of the network. So no, Bitcoin is not an oligarchy. All of these big addresses likely belong to exchanges like CoinBase, etc.