I think that a politically motivated group trying to disrupt our grid is a possibility that has to be considered. After all, the article does cite the case of three men recently convicted for just that.

But the article describes a variety of different attacks, and it's not clear to me all of them are planned with political motivations. It seems just as likely that some of them could be unrelated acts of vandalism from the same types of people who shoot up road signs or start fires for fun. And metal theft is another possible motive for the cases described as using hand tools and chains.