From what I've read, the Target crack was funnelled through a 3rd party HVAC company that did not secure their systems sufficiently.
They may have done more AFTER the scripts gave them access. But it appears that the scripts gave them the initial access.
Where did it actually say that? They know the credentials given to Fazio were used to access the Target systems as the point of entry, but they don't know how the miscreants came into possession of them. The most likely method was a spear phishing attack that allowed a keylogger on to one of the PCs at Fazio. It's simply too far fetched to think that someone trolling with a script happened across Fazio, then just realized they could use it as a backdoor into Target, and then also be in possession of some very sophisticated malware that, oh gee look, matches the Target POS systems exactly down to the firmware rev number.