After World War II, the French government seized the race from the previous owner, who had collaborated with the Nazis. Then, in 1956, Émilien Amaury, the founder of Le Parisien Libéré, another newspaper, and a partner bought the rights, in perpetuity, for 20 million French francs, according to Alex Duff, author of “Le Fric: Family, Power and Money: The Business of the Tour de France.” That is the equivalent of about $700,000 in inflation-adjusted terms, a huge number for a trophy asset that in the days before television was losing money.

In 1965, Mr. Amaury bought out his partner’s stake, and he was succeeded by his son, Philippe, who died in 2006, leaving the company in the hands of his widow, Marie-Odile. By all accounts, she is formidable and unyielding.

In the late 2000s, a Belgian sports entrepreneur, Wouter Vandenhaute, teamed with a private equity firm to propose a modernized cycling league with a full season and the Tour as its Super Bowl. The idea went nowhere. Mr. Vandenhaute offered Mr. Duff a theory about why he had failed.

“It was the French culture of conservatism that stopped any progress,” he said.

That culture has been called “economic patriotism,” an idea reinforced in 2005. That year, the government quashed a rumored takeover of Danone by PepsiCo, calling the yogurt maker an “industrial treasure.” The bid never materialized.

For his book, Mr. Duff got a rare interview with Jean-Etienne Amaury, who took control of the Tour when his mother stepped back in 2020. During the conversation, Mr. Amaury ruminated about one of the offers he and his family had deflected, this one purportedly from a group of billionaires in Silicon Valley.