I wouldn't call them innocent if they legit wanted foreign countries to attack theirs
I would coz that's what they were, innoncents and unaware, the only traitor was the one who lost his hand , he clearly said it in the newest chapter, he was about to tell them about his plan but he didn't have the time to do so because the knight's arrived before that. He was also the only one visibly anxious about his arrival so had the knight not blindly killed them all he'd have known they weren't part of the plan but nope he just raised his sword.
Yeah, those other people looked like scholars/researchers and probably just wanted to share their discovery. The main person plotting treason was eventually left alive while they all died... its really unfair.
Woah this is horrifying, he literally just killed a bunch of innoncent people in a blink of an eye like a damn emotionless robot (⊙…⊙ ) and the worst thing is that the only person still alive is the real traitor.