It’s understandable why Disney might want to bring in an African-American director to direct Black Panther and while Ava Duvernay tells Collider she’s not entirely sure why Disney wanted her specifically to direct A Wrinkle in Time, she does suggest that the fact that the lead character of the book is female, might have meant they were looking for a female director.
With Niki Caro on board to direct Disney live-action Mulan remake, the idea certainly makes sense.
While the world of film directing has been overwhelmingly white and male, it seems that Disney had made a decision on their own to change that with at least some of their projects.