Other mistake: When Padget supposedly tears out his heart with his hand and keeps it in his hand, one can see that the heart's blood vessels were not torn out but must have been precisely cut with some surgical tool. (00:01:50)
Other mistake: Padget hands over one page of his book to his imagined character who is invisible to anyone else except him. Therefore, the page should hover in the air for an external observer. However, Scully watches his apartment on a monitor and notices nothing strange. (00:38:05)
Answer: As he stated many times throughout the series, Mulder needed Scully to be sober and skeptical. Whenever Scully's skepticism wavered and she started questioning her own rationality, Mulder would try to restore her sense of skepticism, because he needed her to be clear-thinking.
Charles Austin Miller