That's pushing it. There's a difference between the character and the performance. Would you consider Morgan Freeman's role in Wanted to be radically different than a lot of his other roles, despite the performances being one in the same, just because the character he's playing is morally repugnant in comparison? I hope not. Yes, the underlying psychological state and morality of the two characters were different, but in the case of Col. Landa, the menace behind the facade was only explored in two scenes through out the movie. Otherwise, they're basically carbon copies of one another, right down to their vocal and physical mannerisms.
What does that have to do with anything? Yes, he acted what he was given but that doesn't change the fact that the end result was a copy and pasted performance from a movie that he already won an award for. Why not give the award to someone who actually carved out a unique performance?