Well they kind of had a monopoly on everything and compromises were made to ensure a peaceful transition of power in a post USSR neoliberal "end of history" world.

Then Mandela's successors got greedy and really screwed up. Ramaphosa (the current president) was supposed to replace Mandela but decided to abandon revolutionary politics, become a capitalist and own McDonalds and the mines instead. This allowed Mbeki, an neoliberal Oxford economics educated guy, to take hold of the ANC, implement austerity measures to make line go up, which messed everything up. Zuma then followed, a corrupt money hungry politician.