2 summers ago when Ninja was really popular I did a back of the envelop calculation on total viewer hours over a year and it was roughly the same as a season of the Big Bang Theory.

Obviously not comparable for a variety of reasons (viewer quality, syndication, youtube clips) but that show was spending 100+ million on just the main cast.

Ninja is really marketable. He has merchandise sitting in Walmart, was on big tv shows like Ellen or hosting a NYC New Years Event.

He's the face of gaming for all the non-gamers right now.

Shroud is just a very good gamer and has a big audience, he's not that marketable compared but still worth a decent penny I guess. He's probably considered the best FPS streamer out there whenever a new game comes out. He's the go to for many.

They are entertaining enough to a big group of people and they managed to build and sustain their audience. It's like asking is Robert Downey Junior the best actor in the world. If you don't see the value that just means you aren't the target audience