I like Kathy's idea also. The basic idea I'm looking at likely wouldn't have done any of A-C, although someone else in the group might have, even the manager. I'm thinking more of an eccentric but playfully jovial drummer than someone cruel and conniving. That may not fit in with the game, but maybe it's just more a personal idea.
Assuming it's the manager that is responsible for all the stuff, I could see something like that Scarie187 is playing the manager, who suddenly disappeared from the public after setting up all this stuff. That way, even if the police ever found out about all the foul play that wasn't accidents as so thought, he's spent months or years covering his tracks and doesn't even seem like the same man. Plastic surgery, fingerprint changes, what have you.
They wouldn't even know any of this at first, they'd just know that some guy knows everything and he doesn't look anything like the one guy who would actually have the information. Of course, since it's Scarie187's character, I can't make it for him but I just wanted to give the suggestion as it came to me. Scarie187, feel more than free to twist that idea and not tell us exactly how if it'd make for a more interesting concept and surprise.
I'll also warn that my drummer idea would probably be more willing to pay the price than to try to cover things up, unless the rest of the band wanted it secret and worked to convince her.
Actually, I just had another idea even if the other doesn't work. Huzzah plot bunnies.
What if the girls had something done to them, whether a magical spell, a brain implant, or whatever, that suddenly made them so spectacular? Maybe it happened five years ago during some common event, which all the girls slowly come to realize as they talk about it that they all remember it differently. The guy coming after them would therefore be the scientist/wizard, who can reliably demonstrate that he can deactivate their talent, and maybe threatens to do so permanently if he doesn't get what he wants.
This provides the humanity, allows the girls to be victims, but also provides owing their success to something outside of themselves. A similar vein would be that the girls were created to be perfect, had fake memories implanted which don't hold up under scrutiny (if they ever try to go back home, nobody they remember was ever really alive), but were deliberately sent out in order to garner up money, fame, and be the perfect test subject for this mad scientist's plan.
Really, I'll follow whatever, but I'd feel bad if I didn't share my brainstorm also.