Evil is perpetually drawn to places with the highest concentration of holiness, as that is its source of energy and vitality.
This explains the talmudic adage “Anyone who is greater than another, his evil inclination is greater than his”(Sukka 52a).
In other words, the intensity of evil’s grip upon a person is commensurate with his level of holiness.
The loftier a person’s spiritual level, the deeper his devotion to holiness, the more invigorated and impactful is the evil drawing its sustenance from him.
Now if the evil inclination is ultimately successful in its mission to destroy the Torah scholar onto whom it is leeched, it no longer has what to gain from his host.
Only too late does the evil inclination realize that he has effectively destroyed his very own source of life.
Rabbi Adin Steinsaltz