"...as for the Why: beyond the obvious financial motivation, it's exceedingly simple... because I can."
I love stories, arts, and honestly, Crossovers, Like Bleach, or Naruto -very VERY little Naruto though...- Harry Potter -LOVE IT!- and more!
It's one thing to create/throw already-established characters in a story of some kind. It's another thing to develop those characters, regardless of the situation they're in.
I love donuts and ponies, therefore i am a dony.