Board Thread:Spoilers!/@comment-24942479-20170422102717/@comment-25536775-20170422113153

The other witches never bothered to fight Zelena; this is consistent with Oz mythos, as the Witch of the North was never powerful enough to defeat the Wicked Witches, and the Witch of the East was wicked. So that's my interpretation. Witch of North is still ruling the Gillikins and Witch of East is either chilling in Munchkinland or dead. Plus, Zelena only felt personally betrayed by Glinda, not the other witches.

Zelena was primarily concerned with creating her time travel spell, paying little mind to the people and affairs of Oz. That means she probably let them starve and cared little for security or external threats; however, this also means she probably didn't actively oppress them like Regina did.