The beginnings of PoS come from a long history of research in distributed agreement in replicated state machines. Going back to the 1970s, many people were working on the issues around making reliable communications from unreliable parts in commercial airlines. A fault in a communication 30,000 feet and with 150 passengers has real consequence so being able to figure out data validity is a life and death problem. From this field of work came the classical Byzantine General’s problem that birthed Byzantine Fault Tolerance (BFT). Up until 1999 (when Practical BFT was invented), the Byzantine General’s problem was mostly an academic one which no one had yet solved. Major computing systems around the world had no practical use for it as banking, stocks, communications, and internet were all centrally hosted and controlled.
It wasn’t until 2008 when Satoshi Nakamoto brought a practical solution to the Byzantine General’s problem into a globally scaled distributed network. This quickly proved to be a stable and secure system to achieve fault-tolerant consensus, causing research in applying these previously academic ideas into real-world applications to explode.