The Nobel peace prize is awarded by a different institution than the science ones. And there are hundreds of people that can nominate, doesn't mean that a nomination reflects anything upon the committee that awards the prize.
Each of the Nobel prizes is awarded by a different committee from a different organization. The Nobel Peace prize was established at the same time and in the same way as the Literature, Physics, Physiology or Medicine, and Chemistry prizes (through Alfred Nobel's will). Of course, by its nature, it is the most political of the prizes.
The only Nobel prize that is separate is the Economics one, which was established much later and has no connection to Alfred Nobel (it is paid for by Sweden's central bank instead of the Nobel estate). But even that one is administered by the same Nobel foundation.
