> Their only purpose seems to be to occupy this domain to counter Nissan the car company.

It's the guy's name. He registered the domain 5 years before Nissan Motor Company showed interest. He seems to have started businesses further and further from "automobiles" so that he wouldn't have a trademark dispute with the car company.

> Their own actual business doesn't look that remarkable or even successful.

Is that the measure by which someone should keep their property?