The funny thing is that this has 3x the views of the official World's anthem performance cause uhh kpop (and Mako)
I think there's a bit more happening than just K-pop though. The video is a great marketing tool. It's music (a genre many like), it's fanservice galore and it's artistically/cinematographically very pleasing. Even my fellow non-gamer, none-anime, none-K-pop privy design classmates were all damn impressed by that aspect when I showed them the video. This video reaches a lot of folks new to the game. Now they know what League of Legends is. Me too actually. I've heard of it before and I've seen some fan arts, but now I am a lot more aware.
It's like those pretty and entertaining Overwatch short films that many like even though they don't like the actual game, just on steroids marketing wise.