First of all thank you for taking the time to corroborate this. Now I'll explain.
Theme:
When the message is heard talking about the killer "developing a parasite that made him crazier" it means that he used it on himself and that is the reason why the game unfolds the way it does.
Diversifier:
The diversifier I used is "Kindness Corrupts" (Good intentions bring bad outcomes) in this case the protagonist appreciates his safety and stays home but utimately that is not enough to stop the Scarecrow Man from attacking.
I hope this provides more clarity, and thank you for reading too.