Maybe because there are no more people to “control” still living there? because last I heard they were turning vast areas of Detroit back into farmland.
The Dingell district now does not include the city of Detroit at all. It includes Ann Arbor, Dearborn, and a bunch of small towns, exurban, and rural areas in the southeastern corner of Michigan. Still should trend Democrat normally, but maybe not this year, considering the local economy.