Why is it in all those Bible movies they seem to cast white actors? I mean, movies like Greatest Story Ever Told and Ten Commandments, get away with it cause they came out DECADES ago, but Exodus: Gods and Kings? Really?
My guess is that the movie studios are more concerned with being a successful business than making good art. As a business that wants to make the most money possible they cast big name actors to help get more people in the seats, regardless of the historical accuracy or ethnicity. Another issue may be that big name actors might have more power when it comes to which movies they do. "If Bale wants to be Moses, let him be Moses!"
And that's the beauty of fan casting! We can let the voice of the people be heard, so any discerning casting directors can reference myCast to for better suggestions.