Detroit was pretty much the place where cars were designed and manufactured in the US at one point in time. The highest producing factories, the engineering, the management, most of it happened practically inside the city. Over time these auto manufacturers opened plants on lower cost of living places, spreading out across the Midwest while a lot of the engineering and management still took place in Detroit.

People often point to foreign competition for the downfall of urban Detroit but the writing was on the wall and decay starting well before foreign imports made a big splash. Between 1945 and 1957, GM, Ford, and Chrysler built 25 brand-new auto plants in the Detroit metro area. Not a single one was built inside the city limits. They weren't building these factories overseas (yet), they were building them in cheaper parts of the US. Detroit lost hundreds of thousands of well-paying factory jobs well before Volkswagen and Toyota started selling things in real numbers in the 1960s.

The great lakes cities were the wealthiest most influential region for a period of time. Go watch movies from the 80s. Detroit was the industrial heart of America.

There are lots of factors but broadly characterizing them as globalization is generally fair. Some included: The rise of japanese cars added competition but they were held at bay by import restrictions and the American preference for massive cars until the gas shortages in the 70s, the trend towards efficient capital meant most industrial firms switched to prioritizing their more profitable financing arms, Reagan liberalized international trade that let foreign imports into the US market, NAFTA moving manufacturing to mexico and canada, companies moving manufacturing to non union states in the south, then moving the parts supply chain abroad.