It possibly is in Russia's interests. If they predict that Europe is on the verge of successfully becoming energy independent and the demise of NS2 through non-sabotage means is all but an inevitability at this point, then it's optimal for them to use that sunk cost for their own benefit, in this case framing the Ukrainians or US in order to turn Europe against Ukraine or to fracture NATO an EU cohesion by stoking distrust.

It's an intelligent leveraging of a sunk cost when most don't realize it's a sunk cost or don't understand the concept of sunk costs.