Not sure about that. Also, I read somewhere that the going rate of solving bank robberies is around 75-80% and many robbers are only caught because a) they do something stupid like not wear a mask or do anything to conceal their identity, or b) continuing robbing banks until their caught.
Considering hacks like this take time and a fairly high level of sophistication, not sure the FBI would want to employ the amount of long term resources needed to hunt these guys down.
The inputs.io hack required zero sophistication. Did you read TradeFortress' explanation? The hacker merely used the password reset feature on an email account, and then reset the Linode Manager password from the email.
Considering hacks like this take time and a fairly high level of sophistication, not sure the FBI would want to employ the amount of long term resources needed to hunt these guys down.