Super fun, super cheesy video makes for great viral fodder, especially the guy in the elevator. It doesn't take itself at all seriously, it's got personality and it's got a lot of comedic elements. You see it, you want your friends to see it. It becomes cool and then people want to be seen as liking it. Then the hipsters will be "I liked it when it only had 3 million views".
The song is infectiously catchy, so it moves to radio.
The dance is fun, easy and becomes a dance of the moment kind of thing. There have been many dances in pop music that have elevated a song, from the Twist, the Nutbush, Bus Stop, Macarena, etc.. I've done a few steps at work in on several occasions and I'm not the only one. Doing that horse thing down the hallway to someone coming the other way is a funny way to say hello in the mornings (yes, I'm that guy).