Keep in mind that the professional class and well educated people in Africa live mostly in the larger cities, and that is the audience for VOA and other world media. Those types of media consumers are more likely to have actual influence over business, education and government.
Russia no longer uses shortwave for its international media efforts. China still uses shortwave to Africa, with broadcasts in English, French, Hausa, Swahili, and Portuguese. However China appears to be placing increased emphasis on satellite television and content provision to local broadcasters on the continent.
VOA and other USAGM services may continue in some form, but I suspect there will be a new focus and emphasis on internet and social media distribution. I fully expect most of the shortwave output will get the ax.
Although China uses SW to reach Africa (as you mentioned), Russia obviously doesn't. The fact remains that both countries are heavily invested in influence in Africa.
Russian influence got several Sahel countries to kick out the French military recently, and replace them with Russian military advisors. China has built infrastructure in Kenya and Nigeria, and is the chief trading partner for many African countries, including countries that have oil and vital minerals. VOA and the BBC can counter that influence somewhat, but not if their internet sites get blocked, which is more probable than authoritarian regimes blocking SW broadcasts. And if people have little or no internet access (as is the case in probably most of African territory), they're not going to get information aside from what their government tells them.
As you're well aware, China's intelligentsia and well-educated people have ready access to internet, being that they -- like those in Africa -- also live in the cities. However, the internet is controlled in China. SW is the only way to attempt to get American opinion, information, and news into China. The Chinese jam the broadcasts because they are aware of the ability for SW to circumvent internet access.
The point behind VOA is to present an American viewpoint that probably isn't readily available in places like rural Asia, Afghanistan, and Africa, especially when 55% of the people are rural and in areas with little if any internet.
Personally, I think Africa is a lost cause when it comes to American interests. However, I don't think VOA's efforts to reach the continent via SW should be curtailed, though. Either the US gives up on the rest of the world, or they don't. Africa is the fastest growing population in the world. Do we attempt to exert at least some influence, or just give up?
Musk seems to think everybody in the fourth world has a cellphone with internet. He obviously hasn't looked at a cell coverage map of any of these countries. Take a look at the Afghanistan one, for example. We still broadcast to Afghanistan for that reason. Radio is the main mass medium in Afghanistan, despite the intelligentsia being in Kabul, where there is decent cell coverage and internet access. The Taliban just closed down a female run station in northern Afghanistan. It's because radio is still a vital influence in areas like that.