>>12760799Botswana and Namibia are basically monocultures. Sudan's problems mostly come the Islamic majority persecuting the Christian minority. The breaking up of Sudan into two states, one primarily Muslim and the other Christian was designed to correct this but the Christian nation (South Sudan) is full of oil that the Muslim nation (Sudan) had been using to fund itself. Once South Sudan broke away, Sudan tried to bully South Sudan into giving up much of their oil. Since the oil pipelines to the ocean go through Sudan, they were able to siphon off much of South Sudan's oil. So for Sudan/South Sudan it's not just an issue of multiculturalism, it's also the resource curse.
I don't know enough about the other nations listed but in general monocultures are peaceful societies and multicultural societies are in constant strife. There are of course some exceptions but the general trend is clear.