How did Muawiyah I become caliph after Ali's assassination?

Following the assassination of the fourth caliph, Ali, in 661, Muawiyah I ascended to the caliphate by leveraging his established military and political power.12

During the preceding civil war, Muawiyah had successfully consolidated control over Syria and Egypt, commanding the largest and most loyal tribal army in the Muslim empire. While Ali’s followers in Iraq initially pledged their loyalty to his son, Hasan, Hasan faced significant internal challenges, including defections and a lack of financial resources to sustain a conflict.23

Recognizing the instability and wishing to avoid further bloodshed, Hasan abdicated the caliphate to Muawiyah in 661 in exchange for a pension and a quiet life in Medina. With this abdication, Muawiyah was recognized as the caliph across the empire, marking the beginning of the Umayyad dynasty and the establishment of Damascus as the new capital of the Islamic state.231