> How was the headline not accurate?

Because it does not provide it's readers with an understanding of what happened, purposefully, to create a more sensationalist headline to generate more clicks and likely more revenue through advertising and subscriptions.

> Because outspoken HN readers assumed this was something to do with government?

First, this is needlessly insulting. Second, it is common knowledge that emissions standards are government regulations (because they are), so titling an article about a car manufacturer about failing emissions standards points _almost everyone_ in the wrong direction.