Came here to say pretty much this. This particular mutation has no selection pressure in its favour in environments where malaria is not endemic. So it can appear and disappear without affecting the overall fitness of the organism. Therefore, it is far from surprising that it appears more in Africans than Europeans, that is exactly what you would expect from a mutation that provides benefit in Africa but not Europe. This is pretty much the same as dark skin being more prevalent in Africans than in Europeans (or, more properly in terms of evolutionary history, light skin is more prevalent in Europeans than in Africans).