My long held argument is Bitcoin is an element of a proof of stake network. While consensus for block production obviously is done via PoW, network consensus actually comes from stakeholders agreeing on the network state. If a fork is proposed and you have two competing chain states then the side with the most pre-fork stake, has the best chance of winning the fork by applying their economic capital to sell off the side they do not want, while buying the side they do with their existing stake. If they also control the world's predominant currency they can also apply their control of that asset to help support the value of the network fork they'd want to win too.