Why did the hobos save Buddha's works?

Each of the texts you've cited were commended to the minds of men in order to preserve knowledge. This knowledge included religions, religious beliefs, religious lessons, philosophy, the sciences, medicine, entertainment, politics.... and everything in between. Montag's society attempted to destroy all the knowledge contained in books, in order to keep their citizens ignorant.... uninterested, unthinkings, and most of all unquestioning. This is why the texts were preserved by the hobos.