It was not in Russia’s interest to blow up the pipelines. Putin may have decided that it was in his best interest. No pipelines means no pipeline revenue should Putin fall to his death up a flight of stairs, or accidentally inject himself with a fatal dose of succinylcholine. The longer it takes to return to the prewar status quo, with Russian Oligarchs back in their London mansions and Mediterranean yachts, the worse the risk-benefit ratio for said Oligarchs considering an attempt on Putin.
Oh, I agree that the USA is the most likely culprit here. Still, the Russians would have reasons to do it too.
Keep in mind that any revenue the Russians would receive from these pipelines would be frozen or held in escrow in Western banks. When you look at it that way you realize that this is not really a loss for Russia.