The reason agreement in principle does not translate to agreement in practice is that the former has no consequences. A contract is not a contract until performance and compensation are agreed. No one is actually going to do anything until their perceived balance of consequences reach a critical mass in favor of doing the thing.
Volkswagon’s values include “social responsibility” and “sustainability”. How then could the company systematically lie about emission test results? Because people agreed with those values in principle and not in practice. In practice, revenue and profits mattered more than social responsibility and sustainability. There were positive and negative consequences to hitting or missing profit targets and none for social responsibility efforts.