Britain was hard to conquer. People were already there and in numbers. They had established but poorly understood cultures, and they fought tooth and nail. They were Barbarians in mud huts. The Rome which was eventually sacked by blonde-haired, blue-eyed Barbarians had long before given up on their civilising mission on an island far away from their centre of the universe. Persia and eventually the Muslim world were more pressing concerns.
Southern Africa was hard to conquer. People were already there and in numbers. I don't know nearly enough about the history of Africa, but what I do know is that the idea that Africa was civilised by the arrival of Europeans is very problematic. Basically it is wrong. In 'Born to Run', the Bushmen of Southern Africa were shown as the last remaining practitioners of one of man's great leap forwards. In developing the art of tracking and being completely in tune with nature, they were able to outrun wildlife even before man had developed decent weapons. Harassing their target till it keeled over with exhaustion. Louis Liebenberg argues that this practice formed 'The Origin of Science' even before we wandered out of Africa and into Europe and Asia.
For most of modern history, the innovation has come from the Fertile Crescent around Syria and Iraq, the Egyptians, the Indu Valley of Pakistan and Northern India, and from the yellow river in China. I live in London. This makes complete sense to me. Until there were lots of things to do inside, the only reason you would live there is if you wanted to be far away from other people. There was wool. Wool helped with the cold. If you really loved wool it was a great place to be, but otherwise you would wander elsewhere.
Western Europeans were for most of history on the periphery of civilisation. The thing with ideas is they spread. Good ideas are hard to hide if you actually want to use them. By the time Europeans were 'discovering Africa' they were very late to the party. A few centuries too late in fact to see Timbuktu at its peak. The nature of the cross Saharan trade had changed, and the libraries and learning of Timbuktu had moved on by the time Laing arrived in 1826. The richest man to have ever lived Musa I of Mali, was the tenth emperor of the Mali Empire. That was in the 12th Century. Roughly 700 years before. Through trade links with Muslims, stories would have spread to Western Europe but all they saw in person were people speaking of the legends. The long history of trade between Asia, the Muslim world and Africa is something I am only starting to learn about.
History is a great humbler. If you think your group more intelligent, you are wrong. If you think your group more righteous, you are wrong. We have all benefited from learning wherever ideas came from, and however long they took to spread. I have still not learnt of any culture that has no dirty secrets. No history of bizarre violence and treating each other horribly. I have still not learnt of a culture that had nothing to contribute.
Africa was very much a part of the Old World. There were mud huts in England. There were mud huts in South Africa. This Soutie (what I get called in SA because I am both British (recently) and South African) knows that I have benefited from the learning from both ends of my being.