The state of the game wasn't good enough (yet) to support this scale of tournament. It's kinda putting the cart before the horse. Relic made a decent foundation, but they didn't to enough for sustainability. Thus, the majority of players have left, which is the main potential audience for tournaments. If they do a good job with ranked, balance, and custom mapmaking, maybe they can turn it around with a vigorous marketing alongside a new campaign DLC.

This is why the (IMO) rushed launch is so painful. If you fail to retain enough of your launch player base, it is hard to regain momentum, especially with a competitive game. You need to invest a lot of time and money to lure people back.