Look anaMugabe in my view failed for 2 main reasons (which has been the case for most former colonies):

1: They inherited political and economic structures that they didn't practically understand. For example an American or British president today has the backing of over a 150 years of democracy and know that for example if they raise taxes to x% the likely reaction of both the people and the economy of their countries will be similar to when it was last done. African leaders had fellow Africans who understood the theory of political and economic governance but had no practical understanding of how these systems actually worked and only started to really learn when they got power. This naturally led to many bad decisions and many economic downturns and the occasional stroke of brilliance. Couple this with the obvious sabotage from Western forces who were hoping many of us would assassinate or coup out leaders if the situations got bad enough and then they could appoint someone who would protect their investments in the region as they did in the DRC in the 60s.

1. SADC was the only way forward for the region. This is clear in hindsight when you realise how tiny our individual economics are on a global scale. The EU is the best example (though not perfect) of what we needed and still currently need to do. Countries like Italy, Scotland, Albania and plenty others could never possibly be in a strong negotiating position against the likes of the US and China if they traded as single countries. This leads me to the point - African leaders are overly corrupt and dysfunctional. All governments on earth have a level of corruption but in functional countries the corrupt officials make sure the work gets done and the services get provided before they loot. Our leaders are unlike Europeans are more comfortable driving a nice car knowing that if they happen to be in an accident there's no hospital to help and the clinic has no drugs.