There has been an enormous amount of “passionate intensity” in the attributions of guilt in the attacks on the NS1 and NS2 pipelines. Some are absolutely convinced that Russia was responsible; others are equally convinced it was the United States. The case of those defending the U. S. isn’t helped by President Biden’s imprudent assertion earlier this year that he would take steps to prevent NS2 from going into production. I think it’s too early to tell. Indeed, we may never know.
One interesting thing I read was that there have been multiple attempts in the past to mine the pipelines using underwater drones. If they discovered who was behind those attempts, their findings have not been made public. All sorts of countries and individuals have underwater drones capable of the job.