The question was asked earlier, "Why do heresies always grow faster?"
An analogy might be drawn with gardens, despite all the gardener's efforts the weeds appear always to grow faster than the cultivated plants. Adhereing to the Truth and maintaining the Ascetic Struggle we are all too easily sidetracked by human pride, indifference and ignorance with the Devil constantly attacking any who might attempt to keep to the Narrow Path of Salvation.
If I might digress, someone in conversation told me proudly he did not believe, nor did he need the emotional and irrational crutch of religion as he was a communist. I quietly asked which communist party did he belong to? He was immediately puzzled. So I began to enumerate the many different and fiercely antagonistic communist parties there were, continuing with the question of in what historic period of time had such fragmentation taken place? My tormentor was neither so arrogant nor self-assured from that point on.
My point is, humans in our fallen state, are prone to fragmentation in almost any endeavour you care to think of including religion.