I don’t see how it makes much sense for anyone but Russia to be responsible. I would expect the US or UK (basically the only other Navies likely capable) could be more subtle than blowing it up with something that registered on seismographs.I do hope this was Russia and not some well-meaning so called "ally" trying to make sure Germany doesn't strike a deal with Russia... otherwise severe questions would have to be asked...
It makes far more sense as a coercive measure from Russia and threat against other pipelines, like those from Norway.