Not sure why you chose the midwest as a qualifier here - out of all the cities you listed, only Omaha would be considered a midwestern city.
Out of the 15 fastest growing cities according to the Census, almost none of them are in the midwest [1] (Only one really: Columbus). Admittedly it's over a short time span.
Also: #5 is LA, a city I don't think anyone would consider to be low cost of living.
The real story is that the south (+ Texas, depending on what you consider Texas) seems to be growing rapidly, not the midwest.
1: https://www.census.gov/newsroom/press-releases/2018/estimate...