One Direction, as well as every other teen pop sensation, is famous because someone at a big production company needed them to be. Acts like these are not grown organically. Most of the time, pop groups and boy bands (n’sync, destiny’s child, bieber, new kids on the block) didn’t start the group themselves, and probably barely knew each other beforehand if they had even met before at all. They were all harvested from the crop of Mickey Mouse Club / Disney Channel child performers and entertainers, then thrown together by a record exec, and had songs written for them by the label.
Songs aren’t “written” as much as they’re “engineered”, basically created and tested in a controlled setting so they can maximize the type of audience response that they’re looking for. The label wants their music to be addictive, and as it turns out they can hire a team of psychologists to work with their composers to make that happen every single time. Its extremely scientific, and theres plenty of literature on it – really, you probably shouldn’t think of it as an artistic process. Its a manufacturing process.
The label then plasters their faces all over everything, and plays their songs everywhere. They partner with every radio station, they partner with TV and movie producers (in a lot of cases, they record label is the same company as the TV and movie producers), they partner with shopping malls and department stores. They want their target demographic saturated with exposure to their product, and they have the financial means to do it. After a few months of this, the teenage girls (the target demographic) are in such a frenzy that their parents are basically tortured into spending money on albums, posters, and concert tickets.
One Direction aren’t a band, they’re the face of a brand thats very aggressively marketed towards young girls for the purpose of getting parents to spend gobs of money, and its incredibly, almost absurdly effective.