"How do you get the malware on the air gapped pc in the first place? The point of air gapping a pc is that it never touches the internet, ever"
The problem with that is it only takes one person to make a mistake, and the Malware is in the system. Stuxnet got into a secure Nuclear facility. From what I understand, all it took was for a Siemens engineer to open an infected document on his laptop at home, then plug the laptop into the secure network. Even just plugging a USB into an infected computer, then into an airgapped computer is entirely possible.