There was widespread outrage at the networks for being so irresponsible:
Much of Trump's dominance of the news cycle is a result of news networks' willingness to air many of his stump speeches and press conferences live, unedited, and without commercial breaks. Veteran campaign reporter Walter Shapiro called the airing of Trump's speeches by networks unprecedented, adding “No one has ever gotten to have all of their campaign speeches broadcast unedited.”
His speeches make for good television -- he calls Ted Cruz a "pussy," imitates Marco Rubio, botches Bible verses, pulls bizarre supporters on stage. But beyond sheer entertainment value, there's rarely a good journalistic reason to give Trump's speeches so much attention.
News networks' inability to look away from the Trump circus means Trump can rely on the media to deliver his campaign messages, unfiltered, to millions more voters than would otherwise hear them. And that special treatment means Trump's opponents in both parties are forced to compete in a news environment that gives Trump millions of dollars in free advertising and exposure.