I agree 100% with you about studying other sacred texts to gain more insight. On this website you can find almost all sacred texts: https://sacred-texts.com/
However, i think that demonology (the study of demons) was not per se studied by evil people, but primarily by the heroes and saints who fought against demons, i.e. against psychopaths and their ilk, in order to know their enemy.
Today this ancient study of demonology would be called "psychopathology" (study of the sick minds) and "ponerology" (study of evil).
I agree 100% with you about studying other sacred texts to gain more insight. On this website you can find almost all sacred texts: https://sacred-texts.com/
However, i think that demonology (the study of demons) was not per se studied by evil people, but primarily by the heroes and saints who fought against demons, i.e. against psychopaths and their ilk, in order to know their enemy. Today this ancient study of demonology would be called "psychopathology" (study of the sick minds) and "ponerology" (study of evil).