beta
My theory
Since the Dowenger Queen said something about her son.
I thought the Duchess was in love with the ML's brother and that he died under suspicious/terrible circumstances.
So she entered into a contact with the ML, she would be his tool and do whatever he wanted only if she could rule in the shadows.
Idk, maybe the death of her love broke her and she decided to get revenge on everyone, no matter if she became a tyrant. And maybe later on she realized her mistake and so let the kingdom fall into ruin.
Only regretting how ML was caught up in it all and his tragic end
So I thought ML had unrequited love for Duchess since she was in love with his brother and missed who she used to be before his bother was murdered. And he entered this contact and played up his role because Duchess told him his mother was still alive.
I want to say ML's mother was accused of his half brother's murder and was "executed" but last second she was switched with a serving girl. The cell she was in caught on fire so the only way they could ID the body was the jewelry she wore.
The Duchess was the one and had plans to end the ML's with her own hands but first wanted to know why she killed her love. Since the ML's mother was always so kind to not only her but her love. She then finds out that ML's Mother didn't kill him and of course she would be framed. Who is the prefect scapegoat to the murder of a prince? The mother of another one.
ML's Mother asks Duchess to bring ML to her and help them so they can escape. She's done with this kingdom but the Duchess denies her. Instead she imprisons the Mother in her estate. She is well taken care of but she's just a bird trapped in a cage. Duchess uses her to make ML side with her.
Even letting them meet once a month
Mother doesn't dare to escape since every attempt Duchess kills a servant or makes the ML take a life. Worse, the moment the Mother tries taking her life that mean she not only forfeits her life but of her son the ML.
I guess the Duchess' end goal was to find the real culprit of her love's murder, why she's greedy for money, it makes tight mouths loose. And building her own power. But she lost her way, ruling the kingdom how she thinks her love wanted, just a twisted justified reason to he a tyrant
BUT SEEING FROM THE SPOILERS
I AM WAY WAY OFF