This has been my pet theory as well. If Apple loses Ives their stock will tank so throwing a couple billion at a car project to keep him engaged is still a good investment (and if they're lucky it might even yield some valuable patents)
Jobs, back when he was still breathing entertained notions of building a car, and I believe that when Tim Cook and Apple's executives make strategic decisions about the company's future, they're still asking themselves "What would Steve do?"