The Chinese culture doesn't allow an employee to have a vehicle (or other similar luxuries) that is nicer than their bosses. Most higher level managers in China's new capitalist economy have a love affair with Cadillac. Keep in mind; owning a Cadillac in China is like owning a Bentley GT here. Given that, China's growing middle class desires a luxury car with a similar "import" status but it can't be better than their boss's Cadillac...enter the Buick. Buick has been GM's cash cow in Asia for the past 5 years or so; I believe they are also building Buicks there. China is the largest growth segment of the automotive market and is now demanding vehicles tailored to their demand.
What frightens me is that China's drivers are the worst in the world. However, I think its only fare that we send them overpowered American cars so they can kill themselves and a few pedestrians since they sent us all of those lead paint ladened tonka toys...and MSG!