One big thing when looking at the internal geographics of these states is that hardly anyone lives there. With a lesser population, things don't become as political and therefore there isn't a high demand for structure and policy. People have their elbow space and prefer this way of life. Guns and religion are what they have as essentials.
Really, that's the biggest factor. Rural communities have a greater sense of individualism and put more importance on personal freedoms. Also, for such spread out communities it's hard for their local government to offer very many practical services. Because of this, they tend to like very limited government involvement in their lives. That's Republicans.
*and you could probably also argue that they are a lot less demographically diverse, which might lead them to put little importance on government intervention to promote and support minority groups.