People differ among themselves when looking at great people, and each one of them takes a standard that is closer to his understanding and more popular among his people. Although some standards are sometimes not related to greatness, you find them popular.
The elements of greatness in Imam Ali - according to the author's opinion - are four: that he is a just imam, a wise and knowledgeable person, an eloquent orator, and courageous in the truth. He tried to highlight these elements in the few pages of his book, and it is difficult to find these qualities in many people other than Imam Ali, and perhaps if you searched for them in a hundred thousand men, you would not find them dispersed among them. Isn't it a miracle then that they are combined in one?