The deck has always been a great consistent deck that focused on control (both graveyard and hand to some extent), and it finally managed to come on top. However, I think this was all possible thanks to Gravekeeper's Recruiter.
By being able to search for any Gravekeeper with a DEF of 1500 or less upon being sent to the graveyard, not only does it speed up the deck, but allows quicker access to Necrovalley via Commandant. And by having valley out quicker, it makes for more consistent Royal Tribute plays. This allows for quicker hand control, as you will most likely be dumping essential cards at any stage of the game (as long as they have enough cards in hand).
However, I'm hoping that this YCS top isn't their only one. I would like to see them make a bigger impact than they did, but even if they don't win again, it would be nice to see them at least get some of the top spots. This meta is quite diverse, but having a classic deck finally top feels like a breath of fresh air. Here's to hoping Gravekeepers do it again!