The country wasn’t gone but many people were. They had either died or fled when the effects of the "Great Potato Famine" dragged on for 5 years.
The wounds still run deep. The Irish people say there wasn’t a famine in Ireland - there was The Great Hunger. Famines result when all crops fail. Only the potato crop had "the blight." Other crops were produced in abundance. It’s just that much of the food (too expensive for penniless people to buy) was shipped elsewhere.