In a nutshell, Mr Christensen’s insight was that it is not stupidity that prevents great firms from foreseeing disruption but rather their supreme rationality. They do “the right thing”, focusing on better products for their best and most profitable clients, often to the point of over-engineering (how many Mach and Fusion blades does a chin need?). But that is “the wrong thing” if it blinds them to the threat from poorly capitalised upstarts offering cheaper stuff in markets too obscure to worry about. Such threats can swiftly turn existential if the rivals move upmarket and go for the jugular.
At the time the insight was radical. To business schools it had seemed obvious that big firms had the resources, the labs and the boffins to out-innovate anyone. “The Innovator’s Dilemma” challenged that complacency. It was also inspirational. It gave startups the confidence to believe that even the best-run incumbents could be overthrown. That may be why Apple’s Steve Jobs and Amazon’s Jeff Bezos were fans—and, once they disrupted their markets, why they stayed eternally vigilant, even paranoid.