The fall of apartheid in 1994 could be best explained because of the collapse of the Soviet Union helped topple Apartheid because there was no longer a threat of communism and the USA had no reason to continue supporting the South African government.
This collapse shifted the geopolitical landscape, reducing the justification for Western support of the apartheid regime and increasing the global momentum toward promoting democracy and human rights, which ultimately played a significant role in the transition to a democratic South Africa.