I think they are worried. When the USA puts their focus on a single thing, usually they can crack the case. See Ross Ulbricht / Silk Road.
That is an incredible understatement. Disrupting key infrastructure would be considered an act of war if it was done by a state actor. I'm not sure what the equivalent characterization would be for a non-state actor.
I do realize that in this case, as reported, the hack involved the IT systems and not the operational systems but I think my point still stands.
Not an easy place to be.