Because of their league and young players. They have so much talents on literally every position. Good coaching, etc. and when you have someone as Egonu you are the top of the World at this moment.
The only problem for me, even if it is a slight one, is Malinov. I don't think she is improving, and her season in Scandicci was a downgrade. But we live in a world with scarcity of wonderful setters, so it is not a great problem for them