Notice how the Nord Stream explosions were timed with the opening of the Baltic Pipe connection, which makes it possible to send Norwegian (and Danish) gas from the North Sea to Poland (and possibly further to Lithuania).
Putin was still trying to energy blackmail Europe back then. It is hard to see the explosions as anything else but a threat that the Baltic Pipe could also be blown up -- and the Nord Stream pipes weren't very useful to Russia at that point so it wouldn't cost much to lose them.
Sorry, but why wouldn't he just blow up the Baltic Pipe then? What use is the threat itself when you admit losing the Nord Stream did cost them something? Seems like a stretch.
That would have been treated as an attack on NATO. Why perform a hostile act if a much cheaper threat works? Even if it only gets you 10% of what a successful hostile act gets you, it is worth doing because it is a lot less risky.
Gotta say this threat doesn't sound compelling. Who didn't know Russia could bomb a pipeline? Seems more like Russia punching itself in the face for literally no reason.
Also, given the climate now, if there was even a shred of evidence or any hint that Putin did this, US media and intelligence officials would be blaring that from every rooftop and every talking head would be "Russia this", and "Russia that". I think the relative silence speaks very clearly.
https://en.wikipedia.org/wiki/Baltic_Pipe
Putin was still trying to energy blackmail Europe back then. It is hard to see the explosions as anything else but a threat that the Baltic Pipe could also be blown up -- and the Nord Stream pipes weren't very useful to Russia at that point so it wouldn't cost much to lose them.