This chapter examines the structural transformation of professional sport into a culturally embedded, entertainment-driven platform economy. It identifies three interrelated layers driving this shift: the rise of the active fan, the move from episodic events to continuous engagement, and the evolution from sports entities to transmedia platforms. These developments are accelerated by two external catalysts: technological innovation and professional investors, which reshape how sport is produced, experienced, and monetized. In this context, diversification emerges as the central strategic response, requiring organizations to balance exploration of new entertainment formats with exploitation of adjacent business opportunities. The analysis demonstrates that diversification is no longer a strategic option but a prerequisite for survival in an increasingly competitive and fragmented landscape. This chapter provides the conceptual foundation for the thematic parts that follow.