If Damon Dailun's deductions were correct, then there were two significant conclusions regarding the Dean:
First, the Deans of Hospital 444 and Hospital 666 were the same "person".
Second, the Dean's real body was not on the level of Hospital 444, but rather within the realm of Hospital 666.
Damon had written a paper on this, it's just that he hadn't had the chance to publish it. In fact, his research had ultimately touched a nerve with the Dean. However, the fact that he was dismissed proved that his views were very likely correct.
Dai Lin and Milan had completely shared memories, which allowed him to be fully aware of all of Damon Dailun's research. He advanced his own research step by step on his own. And the greatest advantage of being the head of the Demons Department was that, even if he researched the taboo topic of "Hospital 444", Damon wouldn't be directly punished by the Dean.
