From Lu Wushuang's perspective, Kong Hui was alone. He was somewhat puzzled as to why you had stopped him rather than taking this chance to keep the Demonic Monk here and pull off another job like when you had attacked the Yijing Feilong Realm.
Yet Lu Wushuang did not directly question you. Since you were the leader of this operation, you had your own reasons for doing so. Even if you might be wrong in the end, he would not choose to challenge you at this moment.
You could not guess what Lu Wushuang and the others were thinking, so you feared they might act rashly. To keep them from making a reckless move, you explained that Kong Hui was not alone at this moment. The reason they could not see his companions was because Kong Hui had concealed them through some method; all of them had merged into the Demonic Monk's shadow.
For someone familiar with Kong Hui, examining the shadow first would make this easier to discover. Yet it was not easy to spot, and those who knew nothing about Kong Hui would suffer a crushing loss. In a place like the Mountain Sea Illusion Realm, Kong Hui was clearly harboring another vile fishing scheme. Theoretically speaking, his chances of success were not low...
With your warning, Chen Jin and Lu Wuyou still noticed nothing. However, they knew their own limits. Their strength was too low, so that was perfectly normal. Lu Wushuang and the Snow Emperor, on the other hand, swiftly noticed something strange about the shadow. Their expressions changed as they realized that what you had said was most likely true.
After Lu Wushuang and the Snow Emperor noticed this, Kong Hui still showed no intention of making a move. Only then did you further use