Our gemara on amud beis argues that even though a born female cohen becomes disqualified from Teruma after relations with a forbidden sexual relation, a Levite or Israelite widow who was once married to a cohen is different. Though she may eat Terumah as a widow if she has a child from him, she will not be disqualified by forbidden sexual relations. Even though the power of the holiness of the Levite or Israelite widow is weaker, as she was not born with her holiness, and so we may argue that surely she should become disqualified, there is an opposite argument. The person who is less holy, is less sensitive to disruption and disqualification:
This is a recurrent theme in holiness, the more holy something is, the more susceptible it is to corruption and defilement. For example, only a Jewish person becomes a conductor of impurity, but a non-Jewish person can touch the most extreme impurity and then still remain pure. It is metaphorically compared to a poor conductor of electricity versus a superconductor, or if you will, a white garment shows stains, while a black garment does not.
Haamek Sheila She’iltos Drav Achai (108:1) states it succinctly:
כל שקדוש יותר מתחלל יותר
Likewise we find the dictum (Succah 52a):
כׇּל הַגָּדוֹל מֵחֲבֵירוֹ — יִצְרוֹ גָּדוֹל הֵימֶנּוּ
Anyone who is greater than another, his evil inclination is greater than his.
However, this is not only in regard to separate people, but also in regard to certain events. Some moments in life are loaded with meaning, and depending on the choice made, it can lead to spiritual heights or the depths of immorality. The Midrash (Rus Rabbah 2) tells us that at the moment that Rus chose to stick with her mother in law Naomi and return with her to Israel, and the moment Arpah turned away, each one sealed their fate for greatness or calamity. Rus eventually met Boaz and became the progenitor of King David. Arpah ending up getting gang-raped by 100 Philistines (and one dog! – The Midrash has a way of making its point!). Rus became pregnant with Oved, while Arpah became pregnant with the monstrous Goliath.
Translations Courtesy of Sefaria, (except when, sometimes, I disagree with the translation .)