Why did the eastern and western churches differ?

A:We tend to think of religious leaders as altruistic men, somehow above the rest of us and dedicated to the propagation of the truth. The reality is that religious leaders can be obstinate, selfish and opinionated, and that truth was sometimes that which suited them. This was certainly the case with Pope Leo IX of Rome and Patriarch Michael of Constantinople, as well as of many of their predecessors.

Over a period of centuries, differences built up between the Latin and Greek branches of the Churches over many matters, both large and small. The most important of these were differences over the introduction of the filioque clause to the Nicene Creed and the ordination of married priests. The issue that really prevented any genuine attempts at compromise was the insistence in the west that pope was the leader of the entire Church.