This isn't a hack in the sense that we normally use the word hack to refer to some sort of breach or unauthorized entry. Lizard Squad didn't gain entry to any Microsoft data or Sony data. They didn't breach any Microsoft systems or Sony systems. They weren't picking the lock; they were barricading the door from the outside eg spamming the severs with fake psn and xbox live accounts to clog it up
The teenager is also being held under suspicion of “swatting” - reporting false threats to police in order to have SWAT units storm to a particular location to cause distress to its inhabitants. In this instance the perpetrator sent a hoax threat warning to US police via Skype.