According to a recent study by the Mercatus Center, the state of Michigan is the fourth heaviest subsidizing state in the United State (only behind Louisiana, Washington, and New York). While some object to the term corporate welfare, it effectively encompasses the broad array of activities the state engages in.
For Michigan, these activities vary from tax-free "enterprise-zones" to tax-free bonds, issued at the behest of the Michigan Economic Development Corporation (MEDC). The incentives that drive corporate welfare (concentrated benefits to producers, disperse costs to taxpayers) are not unique to Michigan. What exactly has led to its intensity in Michigan?
The reasons are varied, but Michigan's long history of corruption in the state government certainly contributed. In addition, Mercatus notes that General Motors, Ford, and Dow Chemical all rank in the top twenty companies for subsidies from state governments. Prominent state corporations and a corrupt government? It all adds up.