Russia benefits if they can spin it as US action, as the damage to US alliance and trust relationships are huge and definitely strategic goals and gains for them. For a while in the beginning, when it wasn't clear that a functioning (but unused) pipeline remained, Russia was off the suspect list. But it turned out the sabotage missed a pipe and that fact keeps Russia high on the suspect list.
As for US, Germany had already given in to the US pressure and nixed the pipeline and made the gas deals. Why would US go and blow it up? It is possible, but makes little sense.
Whoever did this did so knowing that US will ultimately be blamed. Biden kinda set US up for that with veiled threats regarding NS before the Russian invasion. It's either Russia or UK/Ukraine, is my guess.