Sorry but this is something I do know something about and is total bollocks.
Well I don't think it is given that every major sport is receiving massive Tv deals because they're one of the few things watched live by people (who are forced to watch the ads then)
Like this deal, the NFL, the Nba etc etc etc
As this article says:
And in the era of DVRs and illegal download sites, live sports make up some of the only TV programming viewers feel compelled to watch live. In fact, live NFL games accounted for nine of the 10 most-watched TV broadcasts of 2013.
As a result, advertisers in the market to reach a large group of people with the same message at the same time have been willing to pay more and more money for commercials during sporting events. While online channels like Facebook are starting to be able to offer marketers the same amount of reach as television, they can only do so by staggering a brand's message to users over a period of time.
Because of the NFL's unparalleled popularity and unique real-time marketing platform, the price of a 30-second Super Bowl ad has jumped from $3 million to $4 million since 2011, even though the audience for the game has remained steady around the 110 million mark.
But because of those high prices, more and more networks have been trying to get a piece of the pie. In recent years, live sports titan ESPN has faced intense competition from upstarts like NBC Sports, CBS Sports, and Fox Sports 1 for the rights to air broadcasts from the English Premier League, the World Cup, and Major League Baseball. Most recently, ESPN paid $15.2 billion over 10 years for Monday Night football, 73% higher annually than the previous deal.