Here's a comment from the Marketing insider on how the NBA managed to become the strongest sports media brand in digital. While I don't disagree with the points made there (a. the NBA is global and diverse, b) they embrace digital, c) they operate with transparency), I don't think these points are critical (check the article here: https://www.mediapost.com/publications/article/320516/how-the-nba-built-a-winning-digital-media-strategy.html).
In my point of view, the NBA differs from most leagues (football, American football, hockey etc) in this point: They have 1230 games per regular season, plus extensive playoffs. There's so much content, it doesn't make sense to try and limit exposure outside live broadcasts. In fact, action from a minute ago is the ideal piece of content to tune into TV now, and yesterday's content is ideal to advertise a game on TV tonight. Plus: Basketball, by nature, produces highlight plays each game which can easily be compiled into spectacular highlight reels (try this with football/soccer - you need way more "minutes played" to get something spectacular, and in fact you have less minutes played in each league). So they can afford to flood all digital channels with amazing content, which is essentially advertising the next or current live game. Live, realtime, the NBA is as restrictive as anyone, because that's still where the money is made. But outside live, they just have more and better content to distribute than anyone else. In football/soccer, highlights are a media right worth millions. While I believe that using these to advertise live would still be a wise choice (strategically: in order to make fans for the future, tactically: in order to help the live rights holders achieve great numbers/new subscribers), all other leagues simply have other, worse preconditions.