Obama did win, and it was for his commitments to green energy and climate change. It's widely considered bad to award people before they follow through to the end, especially for the nobel committee. I think they were trying to use it as further motivation to keep those commitments, but if anything it's usually the opposite.. at least when they give them to sociopath politicians. Could definitely be worse than Obama though.

Edit: Reading more on it, it looks like it was also for nuclear non-proliferation. I guess both are pretty valid awards for Obama, even if he could have done far more, especially in his first two years.