What do you think contributed to the success of the Arab conquests?

1. The belief of ordinary warriors that after death for faith, the warrior immediately goes to paradise
2. Jihad described in the Qur’an as a justification for violence against other peoples
3. Some peoples and cities were tired of the power that they had before the invasion of the Arabs, and calmly agreed to take the keys from their cities to the conquerors, if they did not force them to change their faith; but they collected only a tax, while managing more honestly and fairly.