This isn't the first such attack. You can bet the big agencies worldwide have been aware of ransomware and investigating. They have been putting evidence together. It only takes a few of the right mistakes on the part of the criminals for them to be figured out. In the long run the advantage is to the police because they can keep looking.

If you want to be a criminal who gets away with it you really need exactly one big action, and at most a few tiny practice runs before the big one. Choose your target well because once the big one is done you have to be done. (and don't do anything copycat - investigations to get the first guy might find you instead)