That gas line goes right into Ukraine, they could have blown it up anytime they wanted safely in their own territory. So I’m not sure that makes much sense. They have not done this previously to avoid angering EU allies funding them, as some still rely on it.
I think more likely explanations are it helps make it easier to strike and and shut down a very important rail route for Russian re supply, it brings the war to the Russian people in a way they can’t ignore, makes Putin look weak, draws Russian troops away from other fronts, and if the land is held gives Ukraine a bargaining chip in any future negotiations with Russia.