Definitely not Russia which was using it as significant leverage over the Europeans.
Definitely not the Europeans who were relying on it for energy.
That leaves the US, with willing help from accomplices of course.
We can squabble about Hersh's credentials - no doubt to be dragged through the mud in the coming days as establishment types attempt to discredit him - but the base case for this is that the US is responsible.
There's still one pipe of NS2 left unscathed; Russia had offered to start delivering gas over this pipe, prior to the winter turning out to be incredibly mild.
So the potential leverage is still there, and would perhaps have been useful had the climate cooperated. Maybe Russia took out three of four pipes just to ratchet up the sense of risk to Europe.