
I don't think he's so completely one dimensional. That's the thing, the grandpa never learnt from his actions and mistakes. We see it from his strained relationship with his kids and grandkids. He never learnt to admit his shortcomings and change his stubborn, obsessive and controlling nature.
And his continued strained relationship shows how the same behaviour kept being enabled by him and everyone around him because he was the royal King, no one had the power to keep him in check, nor the energy really.
He hasn't even had the opportunity for growth so maybe Judith's presence presents an opportunity for him to develop. Also comedy.
Grandpa is such a one dimensional character, few chapters ago he was telling FL how much he regrets what happened with his sister, and now he tries to lock up his granddaughter because she likes someone from family he doesn't like.
She is not his property, she is grown woman, she can do whatever she likes, I wouldn't be surprised if she decided to run away one day and cut ties with royal family, just like her grandma. Grandpa is making the same mistake he did years ago, but he can't see it.
FL just met those ppl from royal family, so she isn't rly attached to them, especially because of old man who tries to control her life and lock her up, so leaving them behind wouldn't be hard for her.
What I want to say is that this old cook is annoying af, he isn't close with his other grandkids, and they aren't rly bothered by it, imo it says a lot about him.