Leadership is a continual problem.
How did leadership get so bad?
Well, to begin with, at the point of independence very few countries had a well-established bureaucratic class that could take up the mantle of leadership. Poor Niger had less than 10 college-educated Nigerien people in the entire country. Even better-off countries only had at best a couple hundred people with any tertiary education. Since any infrastructure was set up for white benefit, it’d be at least a generation before, even in the best of circumstances, there was enough leadership to run a country. Colonial rule had been so tight that many African countries were in a position where no African had ever taken even a mild leadership role. Any functioning local leadership systems were broken or re-moulded to serve colonial purposes.
Note that this is extremely different than the case in India, where the British were less interested in extracting raw materials, and more interested in developing markets for British goods. Markets need a middle class, and Britain fostered one.
Then after independence, a second and more decisive blow to good leadership happened. A wave of young African leaders emerged, full of ideas for their newly free continent. Exciting ideas like pan-Africanism were in the air while dreamer came streaming back from Paris universities and out of the intellectual circles in local capitals ready to lead their countries.
And we shot them. We shot them in Belgien airports. We blew up their planes. We chopped them up and drove around looking for places to dispose of the pieces. When we could, we funded someone else who we figured would kill them. But when worse came to worse, western intelligence forces had no problem doing the killing themselves.
An entire generation of leadership was killed, as a direct or purposefully secondary result of Western intelligence forces, in the era immediately before and after independence.
We nipped African leadership in the bud.
In there place a group of insecure, easily-manipulated leaders that were weak enough to comply with Cold-War plan for Africa were ushered into place. With very little popular support, they were subject to coup after coup, which western powers usually insulated them from. Even in the 1990s, French forces were directly protecting the Idriss Deby in Chad, a leader too weak to even pretend to control more than a few kilometers out of the capital. Because these Cold-War puppets were so weak, they had to rely on alliances with ethnic leaders to even pretend to control their borders. In a lot of countries, ethnic politics is a very new thing, and has come about as a modern way for leaders with no popular support to maintain control of their territory and break up the opportunity for united opposition.
These are the forces that are still at play in modern Africa. The ramifications of Cold-War meddling never went away. Nearly every leader, and certainly most of the worst, are a direct result of this. There is a lot of hope in Africa right now that the rest of Africa can follow the wave of Middle Easter uprisings- which is exactly the same thing (weak unpopular leaders supported by foreign forces as a legacy of Cold War policy).