The Overwatch league is aiming big. With teams rumored to be costing upwards of $20 million it is definitely a market that can only be invested into by the traditional sports organisations.
The terms for the Overwatch league, however are proving to be a deal breaker with the only possible revenues coming into the teams only by 2021. This is for a game that is not really doing too well in the only metric for esports right now : Twitch. Overwatch still trails behind the behemoths of esports in Dota2 and CSGO.
The ESPN article mentions the high prices and the fact that it is an unproven esport right now as the primary reason for people not investing into the OWL.