Basically in the royal family, now and then there'll be born a person who's a genius in all aspects
EXCEPT they'll be so good at things that everything just seem so boring to them
and then, once they find something that trigger their interest, they become so obsessed with that thing that whatever it is will decide how that person's path will go
if it's war, they become a warmongering tyrant
if it's research, they become a shut-in mad scientist
if it's a person, that person became their priority #1
if they never find it, they'll live their life like a doll, ever hollow and unfeeling
In the past, the founder king was basically this sort of person, and his 'one thing' was his childhood friend and eventual wife.
In the original setting, the heroine became the one to trigger his interest.
So obviously since Tia already does that, the heroine already lost this route since ages ago.