It's not. If you actually talk to lobbyists and political experts they will tell you that people react very differently to policies that on paper have the same effect.

Mandating efficiency for new cars doesn't obviously hit you int the wallet every time you fill the tank.

I mean, this is obvious. Energy price increases caused by the Russian war contributed to dozens of governments to get voted out. Yet no one has even run an attack and based on a government supporting efficiency standards. Of all environmental policies, mandating efficiency standards must be the hardest to attack by your opponents.

The fact the fleet targets were implemented in Europe by the European Parliament against the wishes of member state governments, including the German one, tells you everything about the politics of this.