This isn't just a list of highest murder rates per capita, it's got some population threshold- likely the 300k population on wikipedia- which boils down to there being like 5 Republicans that have managed to get elected in large cities.
It is: https://freedomforallamericans.org/highest-murders-in-us-by-...
Edit: To be fair though, it is A list. I'm sure there are others as well, as the authors note, its hard to gather most recent data
So yes, your list is applying some sort of population threshold, which means you are then also just selecting for big cities.