Everyone seems to know it was Russia and is just casting out ideas to find a plausible motivation. I find that completely baffling. For opportunity, consider that while setting up the pipeline needs a weird high-pressure residence and special training, blowing it up takes a fishing boat, scuba gear and underwater explosives. The equipment and training is cheap and available. So, those with opportunity is almost anyon…
I just hope it wasn't the US. That would be a devastating breach of trust for Germany and would backfire badly if it came out. I'm rooting for the Danish anarchists. You basically just need underwater explosives and a boat. You hang the explosives on a long rope, throw it over board like an anchor, and drag it into the pipeline. When you hit the pipeline, you detonate the explosives.
I think that already happened in at least one other instance. [0]
[0] https://www.reuters.com/world/europe/us-security-agency-spie...