“Though your people Israel were
Like the sand of the sea,
Only a remnant of them
Destruction is decreed,
overflowing with righteousness.
God of hosts,
Will make a full end,
In all the earth.”
The answer is simple. Although Israel would have been as numerous as the sand of the sea, only a remnant of them will return from the Exile. Yahweh has decreed destruction in his righteousness. The God of many armies will put an end here on earth. The ruin of Israel is coming. Perhaps it already had come by the time of this writing. In fact, the Israelites were never a large amount of people like the sands of the seas.