I've actually read the history.
But GM didn't need to be prosecuted ~ as soon as US 31 was four-laned and paved with an allweather surface, the central part of the interurban system in the Midwest fell apart like a chicken with its head off.
BTW, I'm just old enough to have interviewed people involved in the various deals that supported an improved road network so we didn't need interurban service.
GM, back in the day, was more like a bird ~ a rather large bird ~ but more like an opportunity feeder than a predatory raptor.