The Bentley Arnage was a luxurious car, but underneath, it was old and outdated technology. Even though it was expensive, it simply could no longer compete against competitors, such as the Rolls-Royce Phantom and Maybach 57. Introduced in 1998, it was regularly updated throughout its lifetime. It was originally powered by BMW engines, but all that changed once Volkswagen Group bought the brand in 1999.
Volkswagen engineers subsequently re-engineered the car and eventually replaced the engine with one from VW. These significant updates helped keep the Arnage current until a new model could be released. This is a classic example of how an automaker can take a current design and significantly re-engineer it to extend its lifetime.