Forget Dangote and the rest of the billionaires, the richest people in Africa are politicians. Africans need to reevaluate and rethink their system, so much power is given to the politicians and without any checks or balances. How can an ex-governor not be tried in court for his mischievous activities because there is a written document that said so who signed the documents is it the populace? They loot millions of dollars and stack them up for their families whereas the masses are suffering.
They even go as far as banning the trading of cryptocurrencies because they feel people might benefit from it. When the world is enjoying it. African needs to be taken to the hospital and given proper treatment because they are moving backward. More strength to their youth as many are still thriving in the harsh environment.
Sadly there is little hope for countries that have not gotten their act together already. Many countries in Africa are either crippled by in-fighting, or (as you say) the politicians are flooded with money from overseas. First it was "western" countries that used to ferment unrest and make major profit from the locals, many of those countries have cleaned up their act a tiny bit - in the form of anti-bribery and corruption laws that apply to their people everywhere. That just left a small void which has since been filled by less than ethical countries like China. China is a rising power and will take advantage of any country that can be useful. They will happily take over assets like ports (which can help their fishing fleets) or mining operations, in return for things like rail infrastructure improvements. These improvements do help, but cost huge sums and of course the officials get ridiculously high pay offs. Cryptocurrency will do a lot to help people in Africa who do not have access to banking and need secure ways to store digital currency, however they do need access to reliable internet services to achieve this as well.