> Disabling them is a means to deal economic damage, not an end-goal in itself.

Russia's goal in attacking Ukraine's energy sector is to make the country ungovernable. They attack the energy sector in winter because they know that causes suffering and hope that will cause the populace to turn against their government or at least against the war. It's not just a matter of causing economic damage, turning off the heat is a means to an end in ending the war in their favor.