Even among the various Robins, Tim Drake (Robin III) is often cited as the easiest to relate to and identify with as he wasn't an orphan, acrobat, or street rat although he became the first one in Identity Crisis.
The creators thought that it could try and save the show's popularity by trying to reach a new, much younger audience by making her lead character, mostly in an attempt to make younger audiences relate/identify with her, which obviously didn't work.