As I understand it, the Exelero was commissioned by Fulda to showcase their new tire. Fulda and Maybach go way back. The tire is supposed to be constructed for cars up to 7,000 pounds. Why you'd need a 200mph tire for such a heavy vehicle, I don't know.
The Exelero is based off a Maybach 57, their big-ass limo of a car. That's why it weighs so much. The proportions are just ridiculous, and I can't wait to see the Stig driving it on Top Gear.