I think those that don't make it don't currently have the credentials to really see what is separating them from the successful ones.

Most musicians, if you aren't the star of your own show, rely on a lucky connection, networking, right place right time, or lucky break to get anywhere. I've spoken with and personally know many musicians who just happened to be a drummer/guitarist/bassist/keyboardist in a city where the next big thing was working on his/her craft. Arctic Monkey's lead guitarist sucks ass, good thing his best friend is Alex fucking Turner.

Most independent stars (meaning are the sole focus of their group, write, record, produce everything) are simultaneously putting 100% of their efforts into 30 different things. They're networking, playing shitty gigs every night, working out, eating right, dressing in nice clothing, connecting with fans, producing, re-producing, then doing it again, writing 100 songs and finding one gem and then working on it for a month to make it perfect. I've been blessed to run into these types of people and hear from other people who know people like that well what their day to day is.

They are a league of their own.

They're special because they were born special. And then worked their ass off. Sam Smith was born with the voice of an angel, but then classically trained until his potential was fully realized. Then collaborated and worked under some of the best songwriters in the business. All grind, but he was born with the knack.