Why are most nations in Africa less than 100 years old?

Most countries in Africa are less than 100 years old due to altruism and greed. Slavery was abolished first in France. Then, when England abolished slavery, there was pressure on the government to end the slave trade. The only way to end it was to gain control of the places where it existed. To do that, England and France had to go to Africa and conquer the areas that sold slaves. To maintain trade, they had to find other products to sell. They destroyed a lot of the landscape getting whatever they could. They did not rebuild the great infrastructure or culture destroyed by the Arab slave traders a few centuries earlier. So the European powers created their colonies to stop slavery. They used them to take commodities and not to better the people or teach the people how to improve their own lot. When the Arab states started giving up slavery it became safe for the old states to gain their freedom. The southern part of Sudan is still suffering from Arab slavers. Its culture and infrastructure are in shambles. Other places have children enslaved and forced into the military. Women are enslaved and forced into prostitution. Only Ethiopia remained free and maintains the old culture. Egypt kept most of its old culture. Those nations stand in sharp contrast to some other nations. So, when it became safe for the nations to become free from Arab slavers, they were made free.