Answer:
Explanation: don’t know all the factors, but some of them were:
The cost of military adventures in places like Angola was becoming unsustainable.
The racial arithmetic on which National Party political calculations were made just didn’t work. It was complex, but was basically that Afrikaners (who would vote for the National Party) outnumbered all other white groups (English, Portuguese, etc) they could safely have them all in an all-white parliament and still dominate it. The white parliament outnumbered the Asian and Coloured parliaments, so the white parliament could dominate the tricameral parliament. And the tricameral parliament, sominated by the National Party, could then outnumber the Xhosa, Zulu, Tswana and other black groups. Except that they couldn’t. The policy was therefore to divide some groups (blacks), while uniting other groups (whites), so that the National Party, with minority support, could dominate everyone. But eventually it became clear that the arithmetic just didn’t work.
The realisation that the “border war” was no longer on the “border”, even though it was still referred to as the “border war” in propaganda.
Following from point 3 - the realisation that an increasing number of white South African military conscripts were no longer prepared to fight, when they real;iseed that they were not being called upon to fight “communist terrorists on our borders” but fellow-South Africans, including school children.