I’ll just give you the answers rather than write a Medium story.
During apartheid non-whites were not allowed to represent South Africa in international sport nor could one have mixed race teams. The Springbok colours thus represented oppression and non-whites would cheer the opposing team (though South Africa was banned from international sports).
Nelson Mandela used the 1995 Rugby World Cup as an opportunity to unite all South Africans — that’s why he wore the Springbok rugby shirt. I remember the celebrations in the streets of Johannesburg when the team paraded with the Rugby World Cup they had won — all races celebrated together.
Rugby has always been big in South Africa — for all races. Black rugby history goes back over a century but was played in separate leagues and clubs until apartheid ended.
And of course we have won another two Rugby World Cups since 1995!