Basically, insider used his credentials as a highly trusted resource to access internal repositories. He then anonymously blackmailed the company, threatening to go public as a "external actor" if the company didn't pay him. The company instead got the FBI involved - which Sharp was aware of because of his role at Ubiquiti. He then lied to Krebs at least once (probably twice) claiming first that a external actor had breached ubiquiti and the company was deliberately covering it up.