Complex sentence: However, the rule of the dynasty was relatively short-lived and the Almoravids fell-at the height of their power-when they failed to quell the Masmuda-led rebellion initiated by Ibn Tumart.
Split into simpler sentences: However, the rule of the dynasty was relatively short-lived. The Almoravids fell-at the height of their power-when they failed to quell the Masmuda-led rebellion initiated by Ibn Tumart.