I work with a guy who is a little like this. He explains things in tremendous detail, even when people are desperately trying to tell him that they completely understand his point. He keeps going. Trying to explain it. Just being clear. And thorough. So that they can understand his point.
My father worked with a guy who, if you went to his office, and said nothing, he said nothing. The instant you started to speak, he started to speak. If you stopped talking, he stopped talking.