Why does one platform company succeed at growth while another does not? Our research on the paths of more than 50 platform companies, including several that have become platform giants, points to four main reasons: Unsuccessful firms don’t systematically consider all growth options; they mistakenly believe they must own the various kinds of interactions that occur on the platform, not realizing that huge growth often lies innotowning them; they overlook options to engage companies that can add value or even disrupt their businesses; and they don’t identify a compelling theme that broadens their scope.