Siddartha was a great teacher of the 6th century BC, the son of an unimportant chieftain who ruled in a valley of the Himalayas. His conversion to his new ideals occurred suddenly.  He elaborated the trinitarian doctrine of Master, Law and Fraternity. 
Gautama forbade his disciples to receive money to avoid hierarchical tendencies.  Later Buddhist worship perverted his teachings and turned him into a divine personage.  Gautama's wife believed in her husband's gospel and she was the founder of an order of nuns.  His son became his successor and greatly spread the cult.  The spiritual awakening of the sixth century did not survive in India and had almost disappeared by the time of the Muslim invasion. 
Brought succor to millions of despairing souls.  His life was much greater than his preachment.  He was an outstanding religious teacher.  He taught the best godless philosophy ever invented.  He taught universal salvation, free from sacrifices, rituals and priests. 
Failed to perceive the personality of God and the existence of souls. 
Buddha directed his ship of salvation directly towards the safe harbor, to the entrance of the creek of salvation of mortals, but there, due to wrong navigational charts, the good ship ran aground.  He hardly believed in the immortality of the human personality.  Buddha was a great man and even a prophet to his people, but he was an orphaned prophet. He knew God in spirit, but not with the mind.  He should have listened to the hermit Godad, a Salemite who passed on the Salem teachings to him. 
See also: UB 94:7.