Because the person on stage had thrown something similar to blades towards Asterion. And though it was too fast for the naked eyes, Ether practically saw it coming in slow motion.
This was also why she shouted to warn Asterion, and even moved to put a shield but she was slower than those blades. And of course for Asterion, like everyone else the attack was too fast.
Plus with Ether's shout, he was more confused and by the time he could fathom anything, the blades were already piercing his body, blood gushing out through his wounds.
The crowd immediately went into a frenzy, but they were quick to recover. Once they had calmed down, they formed a protective human barrier around Asterion, before encircling the person on stage as well.
Once was an accident, but if they allowed this to happen again to their king, then it would be their incompetence.
They all surrounded the attacker, before one of them attacked him.
