It's really, really hard to change an old organization to follow a different business model without effectively firing everyone, selling everything off, and starting over. There's inertia in the various forms of personnel specialties, management style, capital expenditures, and financing. A tiny company can change that stuff in the span of a single email because there isn't anything to unwind, but a big company that has gone to great effort to optimize its existing position and has a lot of stakeholders to appease will run into trouble even if it has visionary leadership that can see the problem.

For that reason, startups can persistently find opportunities: e.g. IBM had a rental-computing business model, so it gave up a big early advantage in the PC market while scarcely realizing it; Microsoft swooped in to occupy the new monopoly on software.