Complex sentence: Maimane was the only candidate for the post of Leader of the Opposition in the National Assembly and was elected as the new Leader of the Opposition, becoming the first black male to hold the position in South Africa's history.
Split into simpler sentences: Maimane was the only candidate for the post of Leader of the Opposition in the National Assembly. As he was unopposed, he was de facto elected as the new Leader of the Opposition, becoming the first black male to hold the position in South Africa's history.