they kept an eye on all the contestants in the tournament and realized Eirth was way weaker than most of them (this was when he was just starting his trainning with Treynar) and came to the conclusion that Eirth had absolutely no chance to win at all, hence all their "support" to not worry if he loses and just try his best. So, when he goes ahead and pulls that stunt, they naturally worry that he's being stupidly reckless, but the king realizes his resolve and stops them before they can say anything.