Hersh didn't just question some narrative. He presented a fanciful story as fact that is full of holes and does not stand up to scrutiny. Those who are motivated to see the US blamed for it seem to be uninterested in whether his story actually is true or not. The truth of what happened and how it happened doesn't seem to matter. They believe the US did it, so they believe Hersh's story.

It's frustrating because having a theory that the US did it isn't unreasonable, and could be discussed. My initial reaction was that the US probably did it, it was only later after more details came out and really thinking it through I came to realize it wouldn't make sense. Though if they did it certainly would not have occurred in the fanciful way Hersh presented. I do not know who did it, while I could put a good theory together why Russia did it and can see they had some motivation, I could also make a good Hershesque story about how some criminal environmentalist group from Germany did it. Or why Poland did it. Or Sweden.

EDIT: Actually when you think about it, with the alternative Yamal pipeline through Poland, and Poland's distrust of Germany. Poland had plenty of motivation! Much more than the US. They have the explosives, they can whip together a few tech divers for an easy 80-100m dive, and they have easy access to the Baltic. But motivation and opportunity is not enough.