Cryptocurrencies do not benefit the economy of a country. It has the potential to profit citizens, but not nearly enough to impact the overall economy of a particular country, at least not yet.
Africa do not just like development but I think crypto organizations are increasing in Africa, how about exchanges that can be developed, they will pay government tax and they will employ many workers. Not only that, anything related to bitcoin and other cryptocurrencies in which people are employed all contribute to economy.
Thats a good way, but very few African countries have announced their legal status about cryptocurrency usage. By the time Exchanges to be registered within the country and letting them to operate won't give hands. Even in Nigeria and other African countries, there is big rise in the usage and number of holders.