Its basically a reflection of the way the County boundaries are drawn between Milwaukee and WOW. Milwaukee County has not only the city of Milwaukee but also a large proportion of the cities inner suburbs. In general, only the outer suburbs are left in the WOW Counties. Overall, across the Country, inner suburbs of large Democratic cities have been trending Democratic way faster than those same cities outer suburbs. Its comparable with the difference between Chester and Lancaster Counties, Pennsylvania.
it’s really not though...lancaster is hardly within the philly sphere, while waukesha and ozaukee are the embodiment of educated suburbia and have trended substantially democratic recently (brookfield is 15 minutes away from milwaukee)