They cannot. I don't keep up much with South Africa, but when I do see stories about it, I notice they all involve serious degradation and decline in South Africa's ability to maintain a civil society.
They can't keep the water on. They can't keep the electricity on. They can't stop massive amounts of murders. They are going to disintegrate into Liberia or Haiti within the next decade.
The government of South Africa doesn't know how to govern, but they are pretty good at looting and bribery.
I think you've narrowed it down perfectly.
At this moment, it's unlikely that the South African government is going to be able to organize behind a strongman like Mugabe.
They're too incompetent and corrupt to do anything.
Of course, things may change quickly.
But if you have money, you'll be able to afford living in a gated community with private security.