Give him grace he doesnt know about emotion...
There's another comment that explained it and i also replied on that one, but when we think about it, it's not just because he doesn't "understand" emotions, is more like he still can't grasp the idea of "grieving" someone. Human see "death" as a form of losing someone they love, imagine you can't see your love one even for the last time of their breath.
Meanwhile the prince here, see the concept of "death" as a soul crossing into the after life and the left the world behind as something "good" cause that means they don't suffer anymore in this world, remember that he's not fully a human, he maybe some short of god or a deity. He saw his family member suffering from illness and etc and thought that "death" is not a final goodbye but as a concept that frees the soul that is suffering in the world
I like this explanation your so right
Niiiii, why would you think this would be happy news