He's not smart the daughter the stupid one
I don't think so. It's not like Astelle have prediction powers to guess what his dad plans. After all no one would suspect that the sword will be poisoned & the emperor participate in disguise so they didn't prepare a tight security
She have you know why? Cuz she know her dad is a snake! Everything he did to her and her brother in the past and still didn't learn from that?
She knew who's the suspect, why hesitate? If she can't see any evidence against her father, then she should create one. Her father is playing dirty, then she should make dirtier.
She is just giving him more advantage by just following him since she is afraid. He is not smart, she is just stupid.
I hate to admit but his j*rk dad is surely smart on scheming things (like Moriarty). The first time is when he create a scenario for the trial and solve the issue himself, to make the emperor indebted to him. And now, he sacrifice his daughter to distract the emperor then frame the crime to that silver haired boy (through replacing the sword).
Not to mention he attempt to kill the emperor multiple times (before the Theor reveal) but still manage to slip.