In Michigan, any injuries you get while in your car (and your passengers as well) are 100% covered by your Auto insurance. That is why it is higher.

So the newer the car, typically the lower your insurance. Which may seem backwards since it's "Car insurance" and you may have a shitty old car. It's expensive because you are more likely to get hurt in a car accident if you have an older car.

That being said.

If your primary residence is outside Michigan then you don't have to register or get insurance here. Like if you live in Florida for the winters and only come here for the summer. But you have to legally have your primary residence be outside of Michigan. And you have to spend less then ~100 days here a year. And your primary Health Insurance has to be provided from the state of your primary residence.

If your primary address is in Michigan. And you have California auto insurance. And you get hurt in an accident. You will be in debt for the rest of your life as neither of the insurance companies will be legally obliged to pay for your injuries.

If you have a passenger in your car and your primary residence is in Michigan and you have out of state health insurance. Then the passenger of your car can sue you (and win) for all their medical needs, no matter who was at fault for the accident. Oh yeah, Michigan is a "No-Fault" state.