John Wesley on Jeremiah 40:12

Returned - Probably upon the king of Babylon's first invading Judah, many fled, and more as he went on his conquests, over - running the country; and it is likely at the taking of the city, many escaped, and fled into several countries, as they had opportunity, or judged this or that country would be safest; some fled to Moab, some to Ammon some to Edom, some one way, and some another: but when they heard that the king of Babylon had set a governor of their own religion and country over them, they came back to him; and there being few people left in the land, which was wonderfully fruitful, they gathered plenty of grapes, and other summer fruits.