How it happpened, how we finally caught it.
In other words, Volkswagen wasn’t able to produce diesel cars that had the ideal mix of performance, fuel economy, and low pollution. (Or, at least, they couldn’t do this profitably.) So they “solved” this trade-off by sacrificing cleanliness and loosening the pollution controls. And they accomplished this via software designed to deceive regulators. This was wildly illegal, and they got caught.