I seriously doubt that Apartheid ended simply because international sanctions heated up. I'm sure sanctions played a role, but we seldom hear about the internal politics of South Africa in the final years of Apartheid. Who were the multiple factions involved, and what actually brought the Apartheid government to the table with the African National Congress? Why did Mandela become the opposition leader? Why was South Africa involved in a war with its neighbors at the time?
and a followup question - the US Civil Rights movement in the 1950's and forward appears to have been timed partly(!) on there getting to be a small Black professional/middle class post-WW2 and a slight loosening of social constraints. One could demonstrate in the South (or Chicago) and be mistreated pretty severely, but not so bad as the arson and more numerous murders that would have been the result 4 decades earlier. Did Mandela and the South African movement happen when it did in part because of any modest economic/social progress like that?
In his Long Walk to Freedom, Mandela's description of his education and early legal career suggests they had it even worse, but the plural of 'anecdote' is not 'data.'