Europeans claimed to bring civilization and economic development to their colonies, but this economic development focused solely on building infrastructure to get resources and export them. Now, whether European powers deliberately sabotaged development in Africa is a hot-button topic we're going to stay well away from, but this much is inarguably true. When the Europeans left, African nations did not have the institutions necessary to thrive in the post-war industrial world. They had very few schools, for instance, and even fewer universities. Like when the Congo achieved independence from Belgium in 1960, there were 16 Congolese college graduates in a nation of 14 million people. Also, in many of these new countries, the traditional elites had been undermined by imperialism. Most Europeans didn't rule their African possessions directly, but rather through the proxies of local rulers.