As stated numerous times in recent years Seymour Hersh has fallen into the deep end of conspiracy theories and making up pure bullshit. As proven already by Bellingcat in 2017 when he was making up pro Russian bullshit in Syria

https://www.bellingcat.com/news/mena/2017/07/04/opcw-just-trashed-seymour-hershs-khan-sheikhoun-conspiracy-theory/

There's a reason the media ignores it. Show me another source that isn't based on the ranting of a single lunatic trying to stay relevant. No one, and I mean absolutely no one has been able to verify his claims

The pipeline was useless to Russia as it was never going to open again. It was just costing Gazprom tons of money. At least this way they could gage the Wests reaction to sabotage and see what they could get away with. Europe doesn't need Russian gas anymore, it has no purpose as leverage