Sometimes the best decks end up being a collection of cards that are simply too powerful. Synergy isn't as important as having the best curve and ensuring you topdeck better cards in the lategame.
Siege Rhino has already made a strong showing in Modern because it's good against U/R Delver and Burn, but another card that is pretty good against both of those decks is Voice of Resurgence. There doesn't seem to be a great home for it outside of Birthing Pod, but perhaps we shouldn't be looking that hard. Overall, it's just a great card that can slot into many decks.
The rest of the deck is mostly standard Abzan fair, albeit with a splash of Treasure Cruise. Whether you play Jund, Abzan, B/G, or four colors depends on how creative you want to get with your manabase. In this case, Kurtkeoki cut Liliana of the Veil in order to cast Treasure Cruise, and that makes it much more realistic.
It's hard to argue against playing a deck that has some of the most efficient cards in the format, especially when the manabase appears to be relatively stable.