Complex sentence: During the earlier part of Abu Sa'id's reign, the distinguished Judeo-Muslim scholar and Vizier Rashid-al-Din Hamadani was beheaded, which left the emir Chupan as the de facto ruler of the Ilkhanate.
Split into simpler sentences: During the earlier part of Abu Sa'id's reign, the Judeo-Muslim scholar and Vizier Rashid-al-Din Hamadani was beheaded. This left the emir Chupan as the de facto ruler of the Ilkhanate.