Well as people mentioned the Anime played a big part in her charactors success, I never watched the fillers so her popularitiy took me by surprise as well. Another factor is a VA that voices Hinata, she pretty much became VA royalty with her success as Fate in Mahou Shoujo Nanoha, I beleive her popularity extends beyond anime and she has a highly successful music career. It probably helped further that Hinata actually looks a bit like Nana Mizuki, and I'm sure SP exploited that further by making the anime charactor look even more like her.
From what i understand this has also backfired for nana. Because of her popularity they made a character for her in the toriko anime (not the manga) and at one point she was given a filler arc that caused a backlash so bad that the anime was cancelled (the fans have not forgiven her for that and brought it up when Naruto ending happened). For those who don't remember at one point it was a rising star in SJ and had taken bleach's place in the top three and was bound to pass Naruto at some points. Now? I felt i had to bring up it pass success and popularity just to remind people how popular it once was.
Edited by Bail o' Lies, 01 September 2015 - 01:07 AM.