Read this and answer the question

Uprisings and demands by African leaders led the UN to assume direct responsibility over the territory. It recognised the South West Africa People's Organisation (SWAPO) as the official representative of the Namibian people in 1973. Namibia, however, remained under South African administration during this time as South-West Africa. Following internal violence, South Africa installed an interim administration in Namibia in 1985. Namibia obtained full independence from South Africa in 1990, with the exception of Walvis Bay and the Penguin Islands, which remained under South African control until 1994.

Why did South Africa install an interim administration in Namibia?
internal violence