IIRC Mandela originally was a fierce Anti-Communist, but the Soviet Union made Mandela and the ANC an offer they couldn’t refuse.
That happened in many colonies; the Soviets and/or Chicoms would be the only ones willing to arm those seeking independence (as in Angola, Indochina, Latin America). Ho Chi Minh went to France after WWI to make the case for self-determination, and was rebuffed; the other European colonizers stuck together with France and wouldn’t help. After WWII, independence was inevitable and even Britain had to accept the colonized peoples should have a say in self-determination. While the US supported France militarily in Indochina, Britain wouldn’t (beyond initially helping secure the colony from the Japanese - and Ho Chi Minh - immediately after WWII ended). When Britain made its intentions clear throughout the empire, Rhodesia declared itself independent in 1965 and was then shunned by Western countries (relying on South Africa and Portugal - as the colonizer on both sides in Angola and Mozambique - for aid and trade). After Portugal withdrew from those colonies in 1975, Rhodesia was doomed - the two former colonies became havens for black guerillas, and the Bush War became unwinnable. In 1980 they agreed to elections, but even then there was conflict between the leftist groups led by Mugabe and those who wished for a less-hostile “bi-racial” independence resembling that which Mandela wanted for South Africa (many blacks had fought for the white Rhodesian government during the Bush War, and didn’t want communism for the new state).
I pity those whites abandoned by their governments in former colonies; at one time their governments enticed people to populate them, then decades (or centuries) later they abandoned them. Portugal and France suffered economic turmoil trying to integrate millions of their citizens as they fled Algeria, Angola, and Mozambique - and in a foreshadowing of what would happen in Afghanistan, France also took in many Algerians who had supported them (”Harkis”). The French government wouldn’t allow them in, but their military peers smuggled many out anyway because they (rightfully) understood they’d suffer retaliation if they stayed (many lived in refugee camps for years in France afterwards). When Portugal left Guinea-Bissau in 1975, the new government executed 7,500 Africans who had fought for Portugal; they’d initially been offered asylum with the Portuguese, but refused because they wouldn’t leave their families.
Very sad stuff...