Keep the White Independent Colonies fighting hard. The face of Rhodesia and South Africa were a pampered White minority in gated communities, supported by the brutality of White Paramilitary fighters and Police States. Like 1960s Mississippi on a national level. With groups such as the AWB, it's not difficult to see those nations becoming modern day neo-fascist. Also, keep the Portuguese fighting. Add into that the African natives turning to the USSR (because humanity works in terms of extreme) as a result of various anti-native actions by the West (whatever they may be), the Free World backing the White minorities as a result to keep Africa from falling into the US sphere, and a cluster of proxy wars between West and East in Africa. And heck, let South Africa get the nuclear bomb; so now you have South Africa propping itself by threatening to annihilate its enemies (and maybe it even would try) like a North Korea at the bottom of the world, South Africa guaranteeing the independence of other White minority states through nuclear posturing, emboldening Rhodesia and potential other states (again, Portuguese) and forming something of a coaltion which can extend its influence into the rest of Africa like an oil spill that caught fire.
Just keep twisting knots of extremism and hate and ignorance and anger, with eyes for an eye that make everyone blinder and blinder in constant retataliation, which the parties involved all justify to themselves. All justified evil is is "evil" with an adjective in front of it so people can pretend its something different.
Apartheid South Africa did "get the bomb". They developed nuclear weapons though their arsenal at it's largest point was only like six tactical strength weapons.