Michigan had an opportunity to spend over a billion dollars on transportation a few years back, and used it to add a HOV lane to I-75 in the Detroit suburbs, instead of investing it in light rail and/or busses. As long as the auto industry is here, it'll be ever thus.
While I'm not sure on the timeline, part of that may have had to do with the prior state administration or because of the federal funding / matching funds.
I do agree that more public transportation investment is needed. An expansion/change to the People Mover would be nice now that the main draw to using it is closed and demolished. It doesn't connect to any points of interest other than Greektown.
In a SimCity/Skylines world, the People Mover would link up the Pizza Box, CoPa, Ford Field, Greektown, (existing downtown stops), then swing out to MGM, up to Midtown, and back down the Cass Corridor to LCA. And it would have multiple train cars so you're only waiting a couple minutes.
I'm honestly impressed with the push back MDOT got for the proposed widening of I-94 and M-14. They're absolutely right that light rail from Ann Arbor into the City is needed. Ann Arbor, Ypsi, Willow Run Airport, Detroit Metro, and then express into a metro station somewhere around the Ambo Bridge / JLA that links up to the People Mover?
Fly in. Catch a football game or games, or hockey game, eat in Greektown, and fly out without needing to rent a car?