Sultai is a ramp color, so many lands hit the battlefield, including the lands you play from your graveyard
Sylvan Anthem also seems like a very powerful ending to a chain of Burning-Tree Emissarys on Turn 2, which is the most powerful start Gruul Aggro can have
Whether its Kayas Ghostform which also protects from exile removal or Spider Umbra which gives green the ability to do the same for just one mana its a strategy worth considering
Its adventure can keep your creatures safe for a turn at a fair price, and this cards attack trigger is also great in a deck type that usually goes wide
Not to mention any small creatures from aggro decks, often helping lower devotion
For this reason, I typically begin a game by fetching Forests, but fetch Plains in the midgame to cast multiple spells on the same turn