The most accurate response regarding the end of the Umayyad Empire in 750 is: Discontent amongst non-Arab Muslim converts weakened the empire.
The Umayyad Empire faced significant challenges due to the growing discontent among non-Arab Muslims, known as mawali, who felt marginalized and discriminated against in favor of Arab Muslims. This discontent contributed to social tensions and uprisings, ultimately leading to the Abbasid Revolution in 750, which successfully overthrew the Umayyad dynasty. The other options do not accurately represent the historical events that led to the end of the Umayyad Empire. The Umayyads were not overthrown by Muhammad's forces, nor by the Ottomans (who came later), and they did not convert to Christianity.