Although the country was arguably an island until the 90s, it was economically better off than it is now.
Indeed, and South Africa will remain a
de facto one-party state for the foreseeable future. Mandela did a lot of good at trying to heal the country and prioritised that over economy, etc. And Mandela's legacy means that anyone who doesn't support the ANC is often hounded for being anti-Mandela/pro-apartheid/whatever smear they can get to stick.
Zuma is more Mugabe (and very friendly towards the former dictator and his aims, even if he disagrees with the excesses like lack of democracy) than Mandela though - hard left, often hostile to white people due to the colour of their skin, corrupt.
As far as I can tell, the National Party didn't really trust the black/colored South Africans to run the country, for fear that they would run them (white South Africans/Afrikaners) out of the country.
They just had to look north at Zimbabwe for those fears to be rational (also 'colored' is a specific term in South Africa and the smallish colored population got some of the issues black people got during apartheid, and some of the issues white people have had since - mostly as they aren't one nor the other, and don't have the clout of white wealth or black population and so are relatively powerless).
Though, unlike Zimbabwe, when mobs went around farms demanding whites leave and killing them if they didn't, the mobs didn't have Government backing.
And the actual emigration of white South Africans more resembled (past tense as the white population has stablised now) American-style white flight: crime rates are way too high, the country is too violent now, etc being the reasons why they have left. Also, affirmative action pushed away the less well-off white people as they found it easier to get jobs in other countries (which means the wealth disparity being whites and blacks is still huge, as the whites that are around are the rich ones who could afford to stay)