Dieselgate started as far up the top of VWs fod chain as you can get: the CEO handpicked and protected by the god father himself, Ferdinand Piech. Well possible that Piech was involved in all of that as well. It started as a deliberate decision to limit AdBlue tank volume to safe money, and extend AdBlue usage to the point drivers didn't have to replenish themselves between inspections, which allowed VW to make more money on service.
That cheating was not engineers cutting corners to please management, it was engineers at the very top of management deliberately ordering the organization to cheat.
The TDIs involved with Dieselgate shipped with no adBlue tank. VW claimed to have some special process where they could catalyze the soot without the nitrogen supply to manage it. But that was all a lie.
Adblue (the accepted solution) wasn't added until 2014 at the earliest. The naughtiest thing they did was that the vehicles detected if they were being run in inspection mode, and adjusted the fuel mixture to avoid exceeding particulate emissions. They may also not have been telling people to refill the tanks on cars that had them, but actively circumventing EEA/EPA compliance checks was what infuriated governments.
The engines had AdBlue, tuey reduced AdBlue in the mix when not in inspection mode. Without AdBlue, there was no way to ever meet emission requirements.
That cheating was not engineers cutting corners to please management, it was engineers at the very top of management deliberately ordering the organization to cheat.