Matt Chase for BIReceived wisdom in the tech world is that big, legacy companies are bound by inertia. The more established they are, the more they get set in their ways — and the more vulnerable they are to disruption by a nimble startup. Silicon Valley was founded on the principle that newcomers can move fast and break things — leading to world-transforming innovations.For the most part, though, that's not how it works anymore. Last year, a couple of economists found that venture-capital-backed startups almost never lead to a new company listing on a public stock exchange.