Frank believed that legal decisions are the product, not of legal doctrine, but of the fact-situation presented to the judge. Legal reasoning is just dressing to make it sound good. Moreover, Frank believed that how judges react to various fact-situations is nearly entirely idiosyncratic -- in that sense, it might as well go back to what the judge ate that day, for all the prediction one might do.
But Frank was not actually an academic at all. He was a trial attorney for 20 years, then chair of the SEC, and then a judge on the 2nd Circuit. Which I think makes his legal realist philosophy sound less ivory-towerish -- and more like a depressed drunk:
Let me tell y'somethin'. *hic* I've been, been practisin' law for 20 years. And it's all random. All of it. It's just whatever, whatever the judge thinks is right that day. Law -- you can find law for anything. Judges don't care. They just do whatever they think is right, and who knows what that is. 20 years of practice and it's, it's all random.
Or maybe not.