I don't really care who is behind the sabotage, they would certainly not admit it for obvious reasons, and it could be more complex than it seems.
But the press, here in the UK, in France and in the US, has been suspiciously "clueless", avoiding with great care to imply that anyone in the west could be behind it, even if it really seems obvious that it could very well be the case.
Why? Why are they so careful? They usually are not afraid to speculate, especially on such a scale.
I find it disturbing to think that they could either have received instructions from their respective governments or are simply afraid push any inquiries on this subject.
1. Russia would get income from the pipeline, empowering their economy. 2. This sort of infrastructure would represent increased German dependence on Russia for their energy needs. 3. This would also tend to increase economic and diplomatic ties between Germany and Russia.
Destroying the pipeline (even if it's not being used) could theoretically send the message that these infrastructure projects are not safe and that relying on Russia for energy is strategically unwise.