Rand Paul tried to stop him.
Rand Paul pulls plug on nearly 13-hour filibuster
http://www.politico.com/story/2013/03/rand-paul-filibuster-john-brennan-cia-nominee-088507
Rand Paul launches talking filibuster against John Brennan
https://www.washingtonpost.com/news/post-politics/wp/2013/03/06/rand-paul-begins-talking-filibuster-against-john-brennan/?utm_term=.8316d347969e
He's doing his best in a less than Constitutional friendly environment.
Someone commented yesterday, quite astutely, that people that are placed (yes placed) into position as SOTH are put there because they harbor deep dark bad secrets and therefore take direction very well. Think Dennis Hastert.