The Nintendo World Championships are likely viewed as a successful endeavor for Disney, who aired the competition on their Disney XD channel. Obviously the event was also available for free online, but it pulled in impressive numbers despite this. Here is the official graph:
Overall for all eSports on cable tv, it ranked 20th.
I think my biggest takeaway here is that it had a successful cable debut. My weirdest takeaway is that I had no idea Candy Crush became an eSport, so much so it got several million viewers every single time.
Source: Nintendo Everything