One simple explanation: Goodkind contradicts himself a bunch of times in the series. Part of the reason is that he really is not that concerned with so-called "world creation" (or however he terms it) and moreso in developing Richard to present his philosophy. The other part of the reason is that he's simply not the strongest writer.

To really enjoy the series, I'd advise you to just look past some of the messy writing, and try to enjoy the books for what they are: the story of Richard (and his interactions with others, such as Kahlan and Zedd and Nicci). You'll definitely need to focus on that if you want to make it through the writing mess that is Naked Empire and the Chainfire trilogy.