The Prophet's kind treatment towards Abu Sufyan...
The Prophet's kind treatment towards Abu Sufyan, his son, and his relatives compelled them to hide their enmity towards him. That is because they were afraid of him and eager for money. So after the coming of Islam, the people were about to forget the Umayyads even in their narrow homeland, namely Mecca. As for the battles of conquest after Allah's Apostle, may Allah bless him and his family, the people knew nothing about the Umayyads.
They only knew that they belonged to the Prophet's family and his . Then, after the Prophet, some people, who did not belong to the Prophet's family, were able to take the reins of power. So under their shade, Mu'awiya became the greatest of all the governors in power, words, and deeds. At that time Mu'awiya used his cleverness to make Islam a bridge to cross to power. to corrupt Allah's religion, to enslave His creatures, and to waste the Public treasury.
Allah's Apostle told the Muslims about these deeds of Mu'awiya. These deeds occurred as the Prophet said. So they were among the signs of his Prophethood. Mu'awiya became active during the time of the second and third Caliphs. For they made him a governor over Sham (Syria) for twenty years. So he was able to control the organs of government strongly. In the meantime he fed and bribed the people of Sham (Syria). So they were his supporters there. Accordingly, he was a danger against Islam.
For the people knew that he was from Quraysh (the family of the Prophet, may Allah bless him and his family), and that he was among the of the Prophet. These qualities made him more famous than the foremost , such as Abu Dharr, 'Ammar, al-Miqdad, and the like with whom Allah was pleased, and who were pleased with Him. In this manner the Umayyads came to power again. They began competing with the Hashimites using their name openly. Still they (the Umayyads) plotted against them secretly.
They (the Umayyads) seized the opportunity to deceive the common people with their cunning. In the meantime they bought the prominent people. They showered them with the money that belonged to the common people. Also they gave them positions paying no attention to Allah's will. That is because Allah refused to give such positions to the traitors like them. They took advantage of the conditions of the conquest and the pleasure of the Caliphs with them.
When the Umayyads took the reins of power through Mu'awiya's cunning, they followed satanic methods to corrupt the religious commandments.