African nations made the mistake of leaving their status as colonies to found relatively small nation-states, instead of embracing large federations under perhaps the initial umbrella of the United Nations. Academics and intellectuals, both local and international, supported the move, just to regret it half a century later. Here's what a recent academic paper has to say about it: "From the middle of the 19th century, most of Africa was colonized by Western powers and the continent remained under its European overlords until independence movements gained strength in the aftermath of WWII. The main wave of independence started in the late 1950s and in 1960 alone, 17 countries achieved independence. With the exception of South Sudan, the full process of decolonization and independence was completed when Eritrea and Namibia became independent in the early 1990. In virtually all these countries, the key figures of their independence movements initially became the first official leaders. All promised better conditions for the people and when Africa stood on the edge of independence it was with the hope of prosperity. This positive outlook was shared by Western observers, as described by Easterly and Levine (1997, p. 1203): “In the 1960s, a leading development textbook ranked Africa’s growth potential ahead of East Asia’s, and the World Bank’s chief economist listed seven African countries that “clearly have potential to reach or surpass” a 7 percent growth rate.”
However, what should
have been the start of prosperity for the continent instead became what has
become known as Africa’s growth tragedy. Today,
Sub-Saharan Africa is the poorest part of the world, as a consequence of 20
years of declining GDP per capita. The decline was so massive that the average
1972 GDP level was not reached again until 2004."