By the way, I suspect most people consider Stewart's humor the reason for the great success of The Daily Show under his time with the show. His humor was magnificent and certainly high among the reasons -- it can't be otherwise. But I would suggest that what we see in this video is most-probably the top reason, because it's the foundation of who he is, and informs everything about him, including his humor.
What should not be overlooked is that these words were not carefully crafted and written out beforehand to make sure he would be able to get his substantive points across. That this eloquence is done extemporaneously speaks even louder to it informing who he is.