When she was remotely famous while she was in the movie the Parent Trap, it was no big deal. When she went unnoticed in Bette Midler's recently failed sitcom, no one cared. When she did the cute Freaky Friday, she was cute, but still no big deal. When her movie Confessions of a Teenage Drama Queen bombed, it was no big deal.
Yet when she hit it big with Meangirls, and was seen (by the media and male hormones) and loved, now she's hated.
Asking why LL is famous is like asking why any actor/actresses are famous. It's sort of a redundant question.