I wonder just who at VW was in on the emissions cheating software. It could have be just a single programmer. Despite code reviews, only the programmer, usually a single individual, really knows what his code does. I can visualize a clever programmer thinking up this scheme, and being so pleased with his cleverness that he slips it into production code, without anyone's knowledge.
I can also see someone in middle management thinking up the scheme, and taking it to his boss for OK. And I can see that boss going to his boss, right up the organization until the CEO's office is reached. I can also visualize senior management, a bunch of bean counters, not really understanding what they were being asked to approve.
I can also visualize someone in engineering thinking up schedules of fuel injector settings vs engine RPM, in fact maybe three such schedules, full throttle acceleration, economical cruise, and "idle" Idle being defined any time the car isn't moving. And passing these schedules over to the programming staff, who codes them up without really understanding what's going on.
Or, someone in marketing, scheming to get into the US market with diesel cars, talks to some old buddy over in engineering or the software group about how to get the diesels to pass the much stiffer US emissions tests.
I wonder what really did happen. And will we ever learn?