"What do you need from me?" asked Naruto, flummoxed as to why he was summoned there. "We need thou eyes over the world," replied the mysterious figure upon a throne of stars. "Just watch? Nothing else?" "No, do as thou wish, and take thy wife with thou." "Very well, Lord of Arda."
The Elemental Lands was not the first place Kaguya went to; she had traveled to many lands and one would suit Zetsu's needs perfectly. They needed a docile, vulnerable, and easily controlled jinchuuriki-best way to achieve these outcomes was leaving the child among the peaceful, weak-willed hobbits of the Shire. His plan might have worked if any other hobbit had found the babe.