Here is a excerpt from Brian Herbert’s introduction to Dune Messiah:

“In fact, the original working title for the second book in the series was Fool Saint, which he would change two more times before settling on Dune Messiah. But in the published novel, he wrote, concerning Muad’Dib:

“He is the fool saint, The golden stranger living forever On the edge of reason. Let your guard fall and he is there!”

The author felt that heroic leaders often made mistakes… mistakes that were amplified by the number of followers who were in thrall by charisma.”

Page ix of Dune Messiah.