Notoriety and because he can? Same reasons many hackers do what they do.
I'll concede that I wish he was doing it for the love of the music, but I don't think anyone who seriously loves music takes the charts seriously these days anyway (it's largely just recycled, generic and heavily watered down crap).
Yeah, I'm not trying to downplay what he did. More effort than he implies but still, mission accomplished.
It's just that he says his aim was:
to be a successful musician in the UK with a Top Five single in the charts
And he's talking like he achieved that, the easy way, with a "hack" no less. And it just doesn't seem to me like he's actually a successful musician yet.
If it were easy, everyone would have hundreds of thousands of Youtube subscribers and more video views than One Direction.
edit: OK, so his one direction stat is nonsense. It's still not easy.
The difference is: if you are building a company you must sustain it in the medium/long term. Zynga/Groupon were hits but see where they are now.
I see this as a way to act if you are a company like Color, only thinking on an acquisition.