The correct statement about the actions of Muhammad and his followers is: They encouraged people to change from worshipping many gods to worshipping one god.
Islam, as preached by Muhammad, emphasized monotheism, calling for the worship of a single, omniscient God (Allah) rather than the polytheistic practices that existed in many cultures at the time. This approach aimed to spread the belief in one God among diverse populations. The other statements mentioned have elements that may not accurately reflect the historical spread of Islam.