Producers had moved the show from January to June to avoid clashing with other events. This was also supposed to enable outdoor events and even test drives that weren't practical during a Michigan winter.
The Detroit gathering has long been an important show for American automakers, not to mention foreign brands hoping to make a splash in the region. More recently, though, it has served as a showcase for brands of all kinds as they venture into electric cars and connected tech. Companies will still introduce new vehicles, including at later auto shows if all goes well -- it's just going to be much harder to see these introductions in person, and there might not be as much fanfare.