Colonialism is part of it, but one single thing that is a major driver of instability and challenges on the African continent, apart from borders, is food. If you read the literature carefully, any time there's food insecurity, it's usually followed by political unrest, and political actors take advantage of it. If you fix food insecurity, chances are you are most likely going to have better stability.
On April 17th, 2024. See this statement in context.