What is the fine-grained topic of the following text: Cobb, I think (without looking him up on Wikipedia) must have been American: something whispers "Bonneville Salt Flats" in my ear, and weren't his cars called the Mobile Something-or-other, suggesting commercial sponsorship of a type that decent fellows like Campbell wouldn't have touched with a starting handle. Only return the topic.
Cobb's nationality and his potential commercial sponsorship in car racing