The security of Tor is built on the assumption that one actor owning a majority of the nodes is improbable to the point of being written off as a non-concern. The tool has always been run and maintained by the USA government. When they opened access to the public, they owned the majority of the nodes, and with the amount of compute available to the NSA (look up the size of their official data-centres, add in their hacked bot-farms), it’s almost certain they still do. If it wasn’t their plan to always have supremacy, they aren’t doing their job. The purpose of Tor is to hide traffic from USA’s enemies. A few tens of thousands of private users is just reducing their power bill and painting targets on their own backs, not successfully hiding from the NSA.