I could be wrong, but I thought "technicals" appeared on the scene earlier than that. Like when Algeria jumped into the Western Sahara mess and supported the rebels when the Spanish left and Morocco took over.
Talking Sub-Saharan nations . . . I don't believe there was one (maybe Somalia?) where a majority of the population spoke the same native language. So in that sense, the colonial powers did give their creations a common national language. The problem was that none of those countries were really ready for independence. Some of them still aren't. But the colonial powers might have solved some problems by doing a better job of separating Muslims from Christians/animists, as well as major tribes that were historical enemies. Stuffing them all together in one country where they've been enemies forever based on religion, history, whatever is asking for trouble. Creating a country and calling it "the land of the south Slavs" (Yugoslavia) didn't work out well at all after strong man Tito died.
