I believe there was said at some point of the manga, that you need to defeat (I think kill) the captain of a division that you wan't to become captain of if you try it by force. I believe that's how Kenpachi got his position. I believe the same was said about Captain-Commander's postion (something along the lines, that there is no one stronger than him, so that's why Yamamoto is still in that position) So maybe this Vandenreich leader was once even the Captain-Commander until Yamamoto defeated him.
