I have been to many Nelson Mandela museums, and spoken with a lot of people who lived through the end of Apartheid. When he took power, both the black and white populations were gearing up for civil war. One guy told me that there were charts up at his school showing the likely kinds of grenades that could be thrown at him. Anyway, Mandela managed to calm things down. He might have been the only guy who could have navigated that exact time period. He did it through a series of policy changes, meetings with key leaders, and speeches. Entirely peaceful, but importantly, there had also been huge amounts of violence leading up to his release from prison and becoming president.

Did the racists change their minds? I don’t know. But the transition to the new government was peaceful.

I would suggest that the oppressors found it no longer beneficial because many of the oppressors' recruitment pool for the instruments of oppression had changes of heart.

I would not count on the 'hearts' of those in power under any circumstances, but if you consider oppression to be imposed by society, then there are many oppressors whose opinions can be swayed, even if violence should not be surrendered as an additional, conditional, or potential tool.

Appealing to moral sense doesn't mean your victory relies on the powerful changing their hearts - sometimes it just relies on their allies withdrawing support.

See, specifically, Ferdinand Marcos fleeing when the nonviolent EDSA protests made him realize he was blockaded on all sides and the CIA would no longer prop him up.