Personally , I think the two main reasons why Africa is poor are corruption and political instability.
Corruption and political instability go hand in hand and are at the root of poverty in poor countries, not just Africa. This is basic knowledge and the OP also made it clear that "corruption" is not an explanation he needs to know because it's something that no one doesn't know. What he wanted to know was the underlying cause behind it all?
Yeah, basic knowledge doesn't cut it when we're talking about centuries of people being taken advantage of. And how money and power still aren't distributed equally worldwide. Colonialism directly robbed those countries and their people. And these systems are still messing them over today, stealing resources and rigging economics so the rich get richer. It isn't just about some bad leader being corrupt or unstable. This whole thing is bigger than that.
Corruption in Africa is just the tip of the iceberg that colonialism wanted Africans to see so they would think that the cause of poverty was government corruption. But in fact, the root of what Africans are suffering is the consequences of colonialism that has been plundering and exploiting Africa since 1880, and they are still doing it today. Not only do they plunder Africa's mineral resources, they also cause illiteracy, seek to prevent education from reaching the continent, and further divide Africa internally...Because only then can they easily plunder without getting a bad reputation, even being seen as the saviors of Africa.
In general, Africa's problems are too complex and will not be solved soon because there are too many forces that do not want African countries to develop because if that happens, they will lose a huge source of resources and income. And not many people will talk about this instead they will focus on blaming the corrupt government and consider it as the cause of everything.
When it comes to poverty in a country, people almost immediately think of corruption and assume that it is the cause of everything. It's not wrong and it's not a secret either, everyone knows it, even a 3 year old knows it. Corruption is not the root cause of all problems, there are bigger causes behind it.
The problem in Africa and the persistent poverty is due to domestic politics being interfered with by external forces, empires and colonialism such as the United States, France, Britain...always trying to interfere and manipulate politics there.
As long as they continue to manipulate and interfere in African politics, Africa will never escape poverty. Politicians are just tools, they don't even have the right to decide their own fate, how can they save their people?