As always, to each their own. The factor that is exists that increases a person’s risk of betrayal is lack of integrity. Any other “factors” in my opinion, are nothing more than excuses.
I think there's a difference between what a WS can say in their defence (which is basically nothing) and what, as a BS or outsider, you can identify as a factor. In some cases there is a stronger tendency toward self-destructive behaviour in a WS than in the BS. They respond self-destructively to stress more than the rest of us. Then there is also stupidity or at least blindness. Among the many reasons I would never have an affair is the fact that I can foresee pretty clearly how terrible the consequences would be. It's the same reason I don't use drugs - in the case of drugs, I have no moral problem with (say) heroin use but the consequences of being a heroin addict are foreseeable to me. Narcissism is another. Some people are more self-focused than others are, sometimes to a pathological degree. WSes are often more narcissistic. Maybe related is a lack of capacity for empathy. Cheats are often just a little further along the spectrum from Mother Theresa to Ted Bundy than other people, even if we are all mostly bunched around the middle. In some cases a weaker personality is a factor; falling under the sway of the AP and the AP's arguments about why it is okay. These factors don't change the grave wrongness of cheating at all but they are factors in a person's makeup that make cheating more likely. They aren't good qualities either of course. And a cheat who pleads narcissism or self-destructiveness as excuses is not going to be well received. But as a BS trying to make sense of it all I find these things relevant to my understanding. They also give me things to look out for as changes in my spouse post-affair. I can't detect integrity too easily but I can see changes in empathy and self-destructiveness. Just to add, thinking about the empathy thing. My wife's empathy vanished during the affair. It was interesting. She became someone who could hear about a school shooting and say yeah well stuff happens, who cares? Whereas previously and since she could cry about a news story involving children. It may be reassuring to you if you can see why your wife's integrity fell short beyond just the integrity itself, because you may be able to see change in other areas more easily than you can see changes in integrity... integrity only really shows when tested but other factors can show all the time.
Maybe it is okay, maybe it will be okay.
BS, d-day Feb 2017, 16 mth affair.