Unlike past research that placed the unit of competition at the individual firm level, recent studies in industrial economics and strategic management have focused on competition at the ecosystem level. Platform leaders who hold dominance in ecosystems possess a superior position over other related firms and can play the game to their advantage. If a platform leader controls the standards that form the core of network effects, it can lead the game with other related firms even more favorably. When a firm possesses platform leadership, a "hold-up" phenomenon can occur in which it captures a far greater share in the industry's value creation process, and other firms may be placed in a "lock-in" state where they lose initiative and simply follow. The position of a platform leader cannot last forever. As a result of technological change or competitive processes, a platform leader may lose its superior position to another firm, and an entirely new ecosystem centered on a new platform leader may be formed. Eisenmann et al. (2011) explained this phenomenon through platform envelopment. This study, based on a historical analysis of the cable TV industry, divided the development process of the cable TV industry into several stages and examined how platform strategies were employed at each stage. In particular, the emergence of satellite broadcasting and the emergence of IPTV were examined from the perspective of platform envelopment. Based on these research findings, the study discussed how future changes in the broadcasting and telecommunications market would affect cable TV platform operators.