Why did The pope banished the Byzantine emperor from the church because of a disagreement over which religious practice?

The Pope excommunicated the Byzantine Emperor Michael I Cerularius in 1054 due to a disagreement over the use of unleavened bread in the Eucharist. This dispute symbolized deeper theological and cultural rifts between the Eastern Orthodox and Roman Catholic Churches. The conflict over liturgical practices highlighted the growing estrangement that ultimately contributed to the Great Schism, dividing Christianity into Eastern and Western branches.