Why are plains predominant in Africa?

The relief of Africa, for the most part, is flat, since this continent has not collided with other lithospheric plates for several tens of millions of years (after all, it is as a result of such collisions that mountain systems are formed). And the existing mountain systems for a long time leveled out due to weathering, so the continent became flat. The only exceptions are the Atlas Mountains, volcanoes along the East African Rift, and several small mountain ranges in the south of the continent.