It used to be, a win on Sunday sells cars on Monday. Torque wins races, horsepower sells cars. The good old days...
Then people realized that NASCAR was about as real as WWE wrestling, that whenever foreign competitors showed up and started winning they got banned, and that NASCAR racing didn’t actually result in better cars but worse ones.
NASCAR actually has retarded the development of American cars because the Big Three dumped money and effort into developing ways to go faster around an oval while everyone else was developing ways for cars to be better in the real world, such as being able to turn right as well as left and having suspensions that could handle rough real world roads.