South Africa is a very unstable country, with a high probability of political instability. Also, the high crime rate means that a disproportionate amount of BTC may make its way to the dark market.
African countries with unstable governments is exactly why Bitcoin is such an amazing alternative. If these countries weren't unstable, the economies there were thriving, why would they need Bitcoin? Bitcoin is an answer to these and many more problems.
As for the dark markets, who cares? Criminals, regardless of where they are, use that whatever offers them the most privacy and convenience. Bitcoin certainly offers convenience, but it sucks hard in the privacy department. It's way more likely that criminals prefer coins like Monero for their illegal activities. Bitcoin's popularity amongst criminals is taking a dive in the deep, and this is just the beginning. Even mainstream media outlets start to figure that out.
Africa as continent offers a lot of potential with how certain countries within that continent made a major jump in terms of technology. People here tend to understimate them, but they just like we enjoy our daily use of our mobile phones, they have mobile phones they can use in combination with crypto too.