Butter Contains a Lot of Healthy Saturated Fats
It was never really proven that it caused any harm.
In fact, recent studies suggest that there is no association at all between saturated fat and cardiovascular disease. Saturated fats raise HDL (the good) cholesterol and change the LDL from small, dense (very bad) to large LDL, which is benign.
Additionally, butter contains a decent amount of short and medium chain fats, which are are metabolized differently from other fats. They lead to improved satiety and increased fat burning.