Here's a good article about the changes, with the above further explained:
In September, The Messenger reported that Fox was negotiating a new postseason tournament to be played in Las Vegas involving teams strictly from the Power 6 conferences (ACC, Big Ten, Big 12, Big East, SEC and Pac-12). The catch in that proposal: The top two teams from each league that do not make the NCAA Tournament would be required to play in the Fox deal. That would leave the NIT picking over the carcass of what is left behind;