South Korea’s top court ended months of political turmoil when it unanimously decided to remove the impeached president Yoon Suk Yeol on Friday, clearing the way for the country to elect a new leader. But the political crisis that Mr. Yoon triggered with his misjudged declaration of martial law in December — and his ensuing impeachment by the National Assembly — exposed a deep fissure in South Korea’s polarized politics that may prove harder to heal. For months, protesters for and against Mr...