Well, I would make the point that after those colonial forces moved in, many of the native populations wouldn't have liked bigger nations coming and controlling them. These nations had to use strict rules and pretty much oppression to keep the people under control and order which led to plenty of rebellions and wars.
when those colonies left they would have been problems with keeping the people in check and establishing control.
In terms of culture, there is and has been historically growing Islamic presence in Africa which has led to plenty of groups such as boko haram and others Iv forgot the names of. Of course the indegionous african people were very war like and tribal like in their nature and running of the places. after the colonials left this has obviously led to rifts amoung different tribes and leaders on who should be running their countrys
