I hadn't heard about that (so please excuse my ignorance), but surely it's just a case of somebody accidentally/intentionally bringing it in on removable storage, like a USB drive, and plugging it in.
yes, the article says that it will put itself onto USB sticks so that it can be transferred out of a walled garden, therefore it can enter the same way.
Not only duplicating itself but putting data from inside the airgapped network on to pen drives so it can escape. I guess the one is useless without the other but this somehow seems far more impressive.
