Russia could have done it in a “burn the ships, no way out but forward” type of move. Putin might have been worried by a coup attempt by a faction that wished to restore gas deliveries. There is a lot of very rich and very unhappy oligarchs in Russia.

That being said, it’s almost certainly done by NATO as a punishment to Germany for having gone against everyone else who told them these pipelines were a dangerous tool of russian influence/blackmail.