Note the position of Rome on the minimap. There were no hidden luxuries in the undiscovered vicinity of the Cumae.
What happened is that I saw his settler arriving from the north-east, and bought the gold tile to the north-east, as well as the tile to the left of the sheep so that he could not get past me. That confused the AI so much that it decided to essentially throw away his settler, settling in a random spot.
Since BNW I've noticed an increase in extremely aggressive forward settling that often doesn't even make any sense.