Linked from
The 27 pages that link to Mu'awiya I, each with the reason it gives.
DamascusRelated: His caliphate made Damascus the capital of a rapidly expanding Islamic state.
Battle of SiffinRelated: Muawiya led the Syrian forces and contested Ali’s authority.
KharijitesRelated: His conflict with Ali set the political crisis in which the Kharijites arose.
Amr ibn al-AsRelated: Amr supported Muawiya in the First Fitna and governed Egypt under him.
Assassination of UthmanRelated: He demanded vengeance for Uthman and used that claim against Ali.
Battle of NahrawanRelated: Ali’s weakened position after Nahrawan helped Muawiya consolidate power.