NBC has been poorly run for quite some time now, and the pure cost-cutting move of bringing Leno back for the 10pm slot could possibly go down as the worst move in broadcast TV history. It was NBC throwing in the towel saying, "ok we can't compete let's spend as little money as possible."
I do think Conan has struggled since taking over the tonight show, they should have just kept the same format/feel of his old show.