An alternative explanation can be any traumatic experience or "big" event in someone's life such as divorce, sickness (fatal or not), arguments that hurt or destroy relationships, etc. In any of these cases, the person's well-being is drastically altered, usually in a negative way even if they had a secure attachment pattern when they were younger. This would alter the correlation between attachment style and well-being later in life. So many things happen in the time between being a child and an adult that so many factors could play into someone's well-being later in life and most likely something else is the cause and not the attachment style.
