Then you are not understanding it. Looking at a map of people not close to power plants would show the same rough picture. People live where people live, of course! But proximity to nuclear power plants has higher incidence of cancer.

What is different about this study that's worthy of a national map is that it's an evaluation of national data, after having first found the discovery on smaller state level datasets.

Try looking a little closer, and you'll find it's not. South Carolina and Tennessee are obvious discrepancies in one direction, as are New York up by Lake Ontario, central Pennsylvania, eastern Washington, and the Iowa-Nebraska border.