1 Nephi 21: 14

14 But, behold, Zion hath said: The Lord hath forsaken me, and my Lord hath forgotten me—but he will show that he hath not.

What would make Zion (Israel) think that their God had forsaken them? Forsaken doesn’t mean simply forgotten; it’s more proactive than that. It’s more like abandoned, or given up on. So what would make Israel believe their god had abandoned them? The most obvious answer is time. And the related answer is apostasy. They had been promised from the beginning that a Messiah would come and rescue them. According to today’s most visible tribe of Israel, the Jews (Judah), they are still waiting for that Messiah to deliver them from their afflictions. So after these thousands of years, generation after generation of Jews waiting for deliverance, and having to deal with episode after episode of persecution, I’m sure they would feel abandoned; they would give up hope. The reason apostasy is related to this is because if they had not apostatized they would have realized the Messiah did come to deliver them, although not from what they thought they needed deliverance, and he was among them in the form of Jesus Christ, whom they rejected. In their rejection of their God, they feel rejected. There’s the irony. But in the end God will show them that He has not forgotten them at all.