I didn’t include the text that went along with the diagram (they eluded to the map stats being related to each state’s gun restrictions) because I didn’t think there was enough evidence that the two were related.
OCRenter’s diagram shows there indeed may be other reasons for the map stats. They may be all related (ie, low gun ownership may mean the residents are more open to gun restrictions, low gun ownership means less weapons may mean less weapon deaths, tighter restrictions may mean less weapon deaths, or some combination of these) but that would take somebody to study it in depth to determine.