They simply could not afford such lethal civil war. They wanted strong government, and Muawiyyah, an able ruler, was able to give it to them. He revived Umar's system of segregating the Arab Muslims from the population, and even though some Muslims in Arabia were still agitating for the right to build estates in the occupied territories, Muawiyyah continued to forbid this.
He also discouraged conversion, and built an efficient administration. Islam thus remained the religion of the conquering Arab elite. At first the Arabs, who had no experience of imperial government, relied on the expertise of non-Muslims, who had served the previous Byzantine and Persian regimes, but gradually the Arabs began to oust the dhimmis from the top posts. In the course of the next century, the Umayyad caliphs would gradually transform the disparate regions conquered by the Muslim armies into a unified empire, with a common ideology. This was a great achievement; but the court naturally began to develop a rich culture and luxurious lifestyle, and became indistinguishable in many respects from any other ruling class.