We can only speculate on this, that merely serves our own amusement. Anyway, I believe they did analyze past work, maybe not all of it, and decided it was not sufficiently sound. Scientific misconduct is never judged by a definition of a few words - a commission is assigned to evaluate the matter, even a small one. After all, whatever the Nobel Committee is doing, taking it down would not serve the science and society any good. Urging them to improve the selection might be more constructive, but again, without really knowing their inner working (e.g. in this 2000 Chemistry case) this won't be helpful, I speculate.