How did this band get so big? Kellin's got a good voice and they have some good songs, but for the most part they're a pretty typical scene band.
A combination of marketability, effort, and good management decisions.
I remember playing with these guys for like no crowd when they had been a band for a couple months, super sloppy, didn't look like a huge band in the making at all. And then a couple years later they're tearing shit up and selling enormously well. Goes to show you what development of young kids can really do.