Why is the Festus, Missouri area so murdery, by episodes?

The Festus area is a scatter of small towns on the southern fringe of St Louis, on both sides of the Mississippi. Festus is about forty minutes from the city, near the river, and grew up beside Crystal City after silica sand found there in 1868 turned out to be right for glass. It was Tanglefoot until 1887, when a local businesswoman opened a Bible and took the first proper name she found.

The other three towns are 20 to 22 miles out: Fenton, Bonne Terre in St Francis County, and Columbia across the water in Illinois, a suburb twenty minutes from St Louis that its episode presents as safe and family-oriented. The deaths are spread out over the same ground. March 1990 in Festus, two cases in September 1993, a farm couple outside Bonne Terre and a single death in Fenton, then a gap to May 2009 in Columbia.

Four episodes, four towns, seven murders. Columbia has three of them, the largest share, and the other towns have one or two apiece. Each town appears once. The grouping is a matter of distance.