After Umar 2’s death, the throne passed to Yazid 2, brother of Sulaiman and third son of Abdul Malik.
Yazid 2 was married to a niece of Hajjaj bin Yusuf. He loved her dearly. After Sulaiman’s accession, Yazid bin Muhallab confiscated her property and persecuted her. Yazid 2 argued with his brother to order bin Muhallab to stop but to no avail. He resolved, if he ever came to power he would cut bin Muhallab into thousand pieces.
Yazid bin Muhallab after hearing about Umar 2’s death bribed the prison guards and fled from Aleppo’s prison. He started his preparation of revolt. From here Yazid 2 sent an army of 80k under Muslimah, who was a Modharite.
Ibn Muhallab died and his brothers and family were killed too. But the consequences were too grave for Umayyads after this event.
This culminated into all-out rivalry between Himayarites and Modharites. The demographics were turning into bloc game. This gave chance to a person named Muhammad ibn Ali to lay claim to the Caliphate from Abbasid.
Hazrat Abbas was an uncle of the Prophet. One of his son Abdullah was an ardent supporter of Ali and Ahl e Bayt. He died with disappointment that he couldn’t do anything. His Ali bin Abdullah, too, didn’t participate in politics.
Whereas Ali bin Abdullah’s son Muhammad bin Ali was an ambitious politician with Machiavellian art.