"33. Supervisors B, C, and F, and others, however, realized that VW could not design a diesel engine that would both meet the stricter US NOx emissions standards that would become effective in 2007 and attract sufficient customer demand in the US market. Instead of bringing to market a diesel vehicle that could legitimately meet the new , more restrictive US NOx emissions standards, VW AG employees acting at the direct of Supervisors B, C, and F and others, including Company A employees, designed, created, and implemented a software function to detect, evade, and defeat US emissions standards.
tl;dr : Bosch (company A) along with VW employees created the evasion function at the behest of supervisors.
[0]: https://www.mass.gov/doc/vw-statement-of-factspdf/download
We know that VW did not write the code. It was the supplier Bosch that did it. VW simply activated a feature through configuration.