> political motivated punishment

You mean, they didn’t like the “politics” of a company installing devices in their cars whose only purpose was to cheat emissions tests, and then afterward lying about it?

Yes, it’s not really so much about the “environment” per se, and more about the criminal cheating followed by criminal coverup.

I think the unsaid assumption, although it is near impossible to prove, is that this was motivated by desire to punish foreign conglomerates and provide a nice advantage to domestic producers. While I'm sure this is near impossible to prove I would be really surprised if lobbyists for the US auto industry weren't trying to get as many sanctions as possible for VW.

The US doesn't really have a pro-deisel lobby, so they were able to impose punishments without internal political pushback.