Can you flesh out your question a little bit? Africa was pretty fully inhabited before the Bantu expansion/migration. The Bantu migration is a combination of replacement of populations and of cultural shift (so, "Bantu" populations expanded both because they replaced non-Bantu populations and because non-Bantu populations were assimilated into Bantu populations.) Both factors are probably associated with technological advantages, particularly ironworking and agricultural techniques. I can't tell if that answers your question.

I just looked, and the Wikipedia article on this is not terrible, although the population genetics findings that it presents are more controversial than the article suggests (bit issue is whether local populations were appropriately sampled).