inb4 this just the "skull company" (I didn't even know such a thing existed) doing a viral marketing campaign. The question is whether it was sent to his public PO BOX (if he has one, like many youtubers do) or to his residence and whether it contained a note or not.
Guaranteed skullsunlimited.com will be getting a bunch of orders from people who never knew such a website/service existed and its novel/niche enough that this would help them stand out.
(I'm seriously not sure if they would attempt this as a marketing stunt, I doubt it given the timing and the fact their name was only uncovered by people investigating the story)