I've only seen the highlights, but from what I saw the kiwis dropped off their foils because they made a mistake by gybing where they did. A bit harder to tell for the Italians, the wind was light so it could have dropped off their foils just as a result of physics. It could equally have been because they made a small error in the tack and because of the light winds they didnt have any margin for error.
The biggest mistake of the day though was probably the Italians sail choice for the first race.