His works was useless in recognizing the 2008 bubble. He may have written some nice papers but when he was in charge he failed completely. He is simply not a good economist and his work didn't help with making good decisions.
He failed at seeing it coming. Once it came, he did really well at damage control. That's not as good as preventing the crisis in the first place, but it's far more than nothing.
First of all, it didn't help him with avoiding a bank run when he was actually put in charge of almost the whole thing a few decades later, which is a thing that happens to very few "Nobel"-like economists (Keynes and his involvement in Bretton-Woods comes to mind, and that's about it as far as I know).
Second, I've always found those Great Depression/New Deal studies a little questionable when it comes to the science of economics, like I've partially hinted in another comment. It looks like the conclusion almost always aligns with the political leanings of those carrying out the study.
Sure, maybe he deserves the Nobel for an interesting work of economic history (or whatever the official term is), but I have the impression that his papers on that period were used as "inputs" for his relatively recent economic decisions, so not as a history artefact.