The Duchess is a failed ruler because she shuts out the political world to establish a private amorous sphere-explain?

The Duchess makes many mistakes because she legitimately believes that withholding information is the secret to her safety in a world where she is consistently spied upon and suspected of inappropriate conduct. Her desire for privacy, the hiding of her marriage and consequent pregnancies, the accusations against her husband and his banishment.... all of these things contribute to her downfall.

Yes

As a Duchess, she obviously had political duties. The fact that she had to focus on her love affair and marriage which was not for a political reason or for the benefit of the people makes her a failed ruler. The reason of death of her 1st husband is not known but we are aware that she is in love with her loyal steward, Antonio. A relationship her brothers do not approve of.

A Duchess with political duties should either have stayed as a widow and perform her duties or her second marriage should be for a political reason. She did shut out the political world to establish her private amorous sphere.

This brings me to question, if she had married for a political reason, or had married a gentleman of the high class, in what likes would you have considered the characters of Ferdinand and The Cardinal.

(These are just in my own opinion, I do not have ample knowledge about the duties of a Duchess and I know that the book is based on a true life story but my question is based on the book and not the truism of the book).

THANKS : )