And let's be honest with ourselves, if they were trying to destroy things (and not... well... terrorize...) then there are A LOT of sectors that are EXTREMELY vulnerable [0]. It doesn't take much knowledge or money to perform acts that would have extreme economic impacts. But wannacry (or something far worse) is less scary than a person shooting up a night club. Terrorists are trying to strike fear, not economical damage. State actors would be the ones trying to do economic damage, but we're not really at war with people that would do that (on a meaningful scale).

[0] a quick google search will lead you down a huge rabbit hole. Here's a good start: https://www.youtube.com/watch?v=pL9q2lOZ1Fw but there's huge flaws in all these sectors and even in cellular communication. Just watch some Black Hat and Def Con conference talks.