Well, yeah. Either he inspired someone else to do it or he did it himself and used the power of STFU and impeccable opsec to get away with it. Here is the timeline.

    On February 12, 2011, Hotz posted a one-minute diss track against Sony

    On April 11, 2011, ... settlement out of court. This included a permanent injunction against Hotz doing any more hacking...

    The attack occurred between April 17 and April 19, 2011... The outage lasted 23 days

    To date, there is no confirmed evidence any credit card or personal information has been misused

"But that's purely circumstantial!"

Yes, deliciously so. This is all thoroughly speculative and had better remain that way.