A number of English and a few U.S. towns have been moved for various reasons. Sometimes for concerns about flooding, often because the business center of town had moved upriver. The factory closed and the people left. It's a major nuisance to move a cemetery and they are usually left in place as the people move away. It's possible the town was dying before the graveyard was abandoned.

Actually, the cemetery and the town are still going concerns. I should mention that the town of Lockeport is basically a rocky little island without a place for a big cemetery, so it was founded a few miles away on the mainland.

You're right about how some old graveyards are left behind after the town or church relocated; moving a cemetery would be a major undertaking (you might say).