Why did the directors make Scabior the head of the snatchers instead of Fenrir like in the books?

Why did they change so many other things?
I don't think they had a reason, just, eh.
A small change- for what, I don't know.

Because Scabior is REALLY FUCKING HOT. :)

Probably because he's one hell of a lot better looking than Fenrir the disgusting creep.

I really don't know. When they make the movies, it's like that have this obsessive need to change crap all the time. It's still a mystery to me on that really.

Because they wanted to?