An interesting paper related to your query is published in Economic and Business History (2022).
The study "TV Demand for the Tour de France: The Importance of Stage Characteristics versus Outcome Uncertainty, Patriotism, and Doping" found that live viewership is largely driven by the specific profile of the stage (mountains vs. flat) rather than just the uncertainty of who will win. Tours Vuelta a Francia en Vivo
It tracks the shift from delayed print-dominated coverage to sophisticated live broadcasting techniques—including the use of helicopters and motorbikes—that changed how audiences perceive the race. Other Notable Studies: An interesting paper related to your query is
The paper identifies three distinct phases of broadcasting: a local French phase (1948–1967), a European expansion phase (1968–1991), and the current global high-quality phase (1992–2021). a European expansion phase (1968–1991)