IBM, at least, made a serious attempt at the PC market during the 1980s. I had two of their machines at one time. But, yes, the startups did eat their lunch.
Two of the companies that became GM, Buick and Fisher Body, were either originally carriage companies or were owned by people who got their start as carriage makers. As for GM, it wasn't really a start-up, but a company that bought out start-ups.This is what usually happens. How mainy railroads, or carriage companies made the transition to automobiles. Studebaker did, for a while, but mostly the new industry was dominated by startups: Oldsmobile, Ford, GM, Chrysler etc.
I'm teaching Environmental Science now, and one of the themes I'm going to start stressing is that there are entrepreneurial opportunities out there. It beats doom and gloom!If green energy becomes the next new thing, Big Oil will go the way of Big Iron. The winners of the current fossil fuel paradigm have every incentive to keep it going.