There are many factors that affect the city being a car production place.
First, the amount of flat land can attract the large manufctors. Car production requires a large amount of space, so they're usually in places with large amounts of flat land.
Second, usually the car production plants are near the source of raw materials. They're near coal fields, or iron markets. These raw materials are heavy and bulky, putting factories near the source can reduce the transport cost.
Third of all, with a lot of car production plants in the same area can prevent them from moving out. This is called industrial interia. They can enjoy agglomeration economies which they can for example order iron or steel together in bulk for a cheaper price or enjoy the abundant labor supply together.
Last but not least, the help of government is important too. Government policies and tax allowances can promote the car munfactors to stay.
