
I guess he wasn't good at it. plus, he had the emperor on his ass 24/7 and Juvel would become a way of threatening the Duke if he showed too much attention. I think the emperor was also already using Juvel against him. It's just pure misunderstandings and miscommunication. Idk why he is showing more affection now, but it might have something to do with the change in persons. Juvel in the past was obsessed with Mikael and only him, so her dad probably just let her be. (This is just what I think, I haven't read the novel sooo)
Spoilers
Also, her death wasn't supposed to happen. Juvel misunderstood the whole situation, but I don't blame her. She didn't know anything and with the way her childhood was, she could only assume she was being abandoned. But, from what I heard, Max (the prince), and her father were conspiring to take down the emperor, so they framed Juvel to put her in the prison because that was the safest place and Max was going to get her and escape. But yk, she kills herself, and I heard that when the Duke finds out, he goes crazy and just kills the emperor.. and I think everyone. I don't remember correctlh so I might be wrong on some parts because I haven't read the novel.
If this duke really liked her, why did he let that happen to her in his last life? It doesn’t add up. Sure he acts differently now, in part because Juvel is different, but at the same time it doesn’t connect.