To be clear, for consumers (of said vehicles), that was actually a negative when they got caught, not while it was happening. The cars were inferior after the software update, because the performance and fuel efficiency balance they offered was never going to be possible with sufficient EGR to reduce NOx to what it needed to be. Many have reported drivability or reliability issues with the updated software unfortunately.

Of course literally everyone else benefited from the fix because air is cleaner now.

While this is totally true, you cannot fault the EU for not acting on the in-house science team info given the EU commission had no authority on policing car manufacturers. At the time that was the duty of national authorities. Now the EU commission has granted itself the power to conduct vehicle audits and fine those responsible. Positives changes over embarrassing scandals are a positive outcome to me, and not the norm in modern politics.

The EU did not prevent Dieselgate because the EU was lacking the regulatory framework to do so. And after Dieselgate, lots of new laws were put into place to address a market wide breach of consumer law (the representative actions directive and the omnibus directive). That is exactly what a good governing body should do: act within the boundaries of the law, and improve the law when something bad happens. I very much doubt it will happen again. We are talking billions in fines before there was an actual framework in place to address this. Today the result could be in the tens of billions.