At what point does a group of people, perhaps thinking they're working to create something good, but that actually results in something that maybe isn't so good, become a "conspiracy"?
The moment it becomes obvious that what they are attempting is impossible and they start looking for illegal ways to circumvent a test. At that precise point they should have stopped and done something else.
There is no real grey area here where people weren't fully aware of what they were doing and at no time were they under any illusion about the legality. The people who implemented this are professional engineers who knew(or should have known) what the rules were and decided to go ahead anyway. This isn't a piece of consumer software where there are no federal laws involved. This wasn't a piece of software where what seemed like a good idea ultimately didn't work. No, they intentionally and with premeditation committed this fraud. Stop it with trying to excuse what they did.
I think that you missed the point of the previous post. It could be that many people involved thought that they were adding a performance function. For example, my Jeep has an ECO mode by default but I can change it into Sport mode for better acceleration.
Granted, at some point it clearly crossed the line. I would say that point was when the wheel spin rate, steering wheel position, etc. were added as triggers. Whoever did that had to know the conditions (i.e. emissions testing) for the trigger to be able to code it properly. But the performance function/mode itself could have started out as a valid feature that they wanted to add to the vehicles. Of course, it all depends on timing. If the triggers were developed at the same time as the performance code then it would be much harder to believe that anyone was innocent. If it was developed separately, then there might be some plausible deniability.