Here's Scott's answer:
I guess being a director, in some ways, is like being the captain of a sports team, like a soccer team, and you have to make sure that you have every position covered really well because that will help you to win the game. So I always look on making a film as a partnership and that's what casting is all about, whether it's the star or the guy with one line. And by doing that you enable them to feel confident to try things out and feel free to suggest things. And over the years I've got the best results from actors who really are my partners in the process and it makes it all the more enjoyable. In this instance I'd met Christian four or five years ago when we had a cup of tea together and a rich tea biscuit in LA and he said, 'What are we going to do together?' And I said "well, I'll come up with something.' And it wasn't until five years later when I was thinking about the idea of Exodus and Moses being this kind of larger than life character who, at the same time, has to be played definitively as a very real person, that I thought of Christian and I knew he was the right actor for the role. It's not a fantasy. Ramses certainly wasn't a fantasy and somewhere Moses is very much written down and indicated and believed. So it's a real thing.
Egypt was –- as it is now -– a confluence of cultures, as a result of being a crossroads geographically between Africa, the Middle East and Europe. We cast major actors from different ethnicities to reflect this diversity of culture, from Iranians to Spaniards to Arabs. There are many different theories about the ethnicity of the Egyptian people, and we had a lot of discussions about how to best represent the culture.