Apartheid SA, ... vanished with little warning,
I just saw this.
There were a lot of signs that the fall of the National Party was inevitable, and this was most recognized in the upper tier of the NP itself in the 1970s. John Vorster's government pulled its unofficial support for Rhodesia after the withdrawal of Portuguese troops from Angola and Mozambique, hoping to avoid further conflict in the region and appease the anti-Rhodesia policies of Western powers.
Domestically, the relative white population was shrinking and poor economic performance left a lot of whites leaving the NP; electoral support of the NP amongst Afrikaners dropped from 85 to 60 percent over the course of two election cycles. At the same time, the ANC was increasingly active in strikes, civil disobedience, and terrorism, driving many whites to support the hardline Conservative Party under ex-Minister of Education Andries Treurnicht (Treurnicht would later become opposition leader in 1987 as the KP became the second-largest party in parliament.)
The NP, now led by P.W. Botha, as Vorster resigned due to a scandal regarding some attempted bribes to international news agencies to plant stories favorable to South Africa, wanted to "rescue" the government by winning over the support of South Africa's other minority groups, Coloureds and Indians. East Asians were reclassified as "white" after the Japan protested when a Japanese athelete was denied the use of a whites-only pool; Koreans and Chinese were also classified as white to maintain friendly relations with the two countries. A new constitution was written and a tri-cameral parliament was establishedone branch for whites, one for Indians, and one for Coloureds. Instead of helping to save the system, though, it further alienated blacks, including moderate blacks whom the government had targeted in trying to "win over."
Violence accelerated in the townships and in a desperate attempt to regain control, Botha declared a state of emergency in many areas. The chaos ensuing in the townships was part of the ANC's strategy to make black areas "ungovernable"local (black) leaders were deposed and often brutally killed. The actions taken by the government, including curtailing some press freedom and imposing curfews also damaged South Africa's international relations. This was unfortunate because at the same time, the NP was accelerating some reforms, but reserving the "big" reforms, such as legalizing the ANC until the ANC renounced violenceMandela was offered a release in 1985 on the condition that he renounce violence, but rejected it outright.
In the late eighties, the situation more or less spiraled out of control and Botha's ill-health led to his resignation and replacement with F.W. de Klerk shortly thereafter. de Klerk would be the one to "end" apartheid in 1990 (though the elections would not take place until 1994.)
So, it wasn't as though South Africa suddenly crumbledSouth Africa, like the Soviet Union was merely destined to fail.