Krugman's contributions aren't widely discussed because they are in the realm of quantitative economic analysis. Heavy in math and not prone to simple explanations. Most of quant econ revolves around trying to use mathematical techniques to derive a more accurate model of what's going on with large scale scale economic aggregates (GDP and CPI are the most well known due to the media).

Of course the critique of the entire field is that it is blatant curve fitting, descriptive rather than prescriptive.

P.S. The nobel prize in economics was not one of the prizes originally enumerated by Alfred Nobel.