Things weren't adding up. Unless Emperor Kong had found a few unparalleled geniuses compared to Wang Wei and had access to merit and numerous other resources that speed up cultivation, there is no way for him to have trained a few Empyreans for the academy — especially given how young it was. All the teachers with this cultivation level should have been people he recruited.
Wang Wei remembered Emperor Kong's life from the sect's record. After ascending, he found a secret realm that allowed him to become an Empyrean in record time. Such an event brought him some fame, but for the most part, Emperor Kong was inconspicuous.