What do you think it is that makes a band commercially popular.

I read about other bands like The Vaccines (who i do like as well) that have gotten pretty big and their story pretty much reads like this "Formed in 2010 and they played a gig in london at the end of 2010 now they're huge" It's not that easy at all! What is the difference between what they did and what other bands do.

Are these bands just super clever or lucky? Because there are unsigned bands that are better.