It's tricky.
One thing that I think gets underestimated by the general public is how picky they are about finding actors for productions. Any group with a fairly small population is going to have fewer actors available to play lead roles. You see it with First Nations actors, there are a limited number of people who can carry a big production, and when it comes down to extras, often they have to cast a lot of non-native people because there just aren't enough available, even just to stand around or whatever. Polynesian actors are also a fairly small group of people.
I remember reading about the casting of the No. 1 Ladies Detective Agency show. They had initially wanted to cast an African actress, and held a lot of auditions and casting calls across Africa. In the end they felt they hadn't found the right person and cast an American woman, I believe.
In one sense that seemed crazy to me, there are obviously loads more black people in Africa, which is a huge continent, than in the US. But I also think there are a lot of things like theater training and experience, facility with English, and other things that come into it.
And then child actors are really difficult - most children are terrible actors, way too hammy.
So maybe it came down to trying to find a child actor who could carry a major film, and the one they found just was lighter skinned?