Complex sentence: He was succeeded by his brother Mu'izz al-Din, who had quickly returned to Ghor from India, and had obtained the support of Ghurid nobles, who crowned him as Sultan of the Ghurid Empire at Firuzkuh.
Split into simpler sentences: He was succeeded by his brother Mu'izz al-Din, who had quickly returned to Ghor from India and obtained the support of Ghurid nobles. They crowned him as Sultan of the Ghurid Empire at Firuzkuh.