Final answer:
The Crusades occurred because the Byzantine and Holy Roman emperors sought help against Islamic empires, and the Crusaders aimed to claim the region for Christianity and drive out Islam.
Step-by-step explanation:
The Crusades occurred because the Byzantine emperor asked for help defending against Islamic empires and the Crusaders wanted to claim the region for Christianity and drive out Islam. The Holy Roman emperor also asked for help defending against Islamic empires, and again, the Crusaders sought to claim the region for Christianity and drive out Islam.
Learn more about Causes of the Crusades