The OP seems to be in almost all cases a necessary part of this process. Someone on the forum once said they don't look for people better than us, they look for people worse than themselves and I truly believe that.
The OP seems to be normal, but let's not generalize about who they are.
They are (obviously) people who have no scruples about getting involved with a married person, but some of them genuinely believe that their affair partner is unhappy in his/her marriage. Sometimes it is true.
OP (old pilot) commented on my thread 4 years ago that my H and the OW were getting their needs met through the R (in this case an EA) and there was nothing I could do except let it run its course. I thought I knew better, but now I see that by demanding it to end, I was pushing them together (just as old pilot had warned me).
The point is, they both had needs. Emotional needs, in my H's case. The OW was similar to him in many respects (though I don't like to think this). She was a perfectionist workaholic doctor like him, with difficulties in intimate relationships. She was callous and manipulative though, and totally lacking in empathy for those she walked over. But hardly a classic affair down. Pretty, petite, clever, successful. And young. Half my age.
But she wasn't me, she didn't make demands on him (the fact that it was an EA meant that there was space for both). She acted like his friend, while making no commitments. My H was the one who was totally hooked on her.
They don't look for one type of person. They look for a person who seems to meet their needs, when they cannot look to us for that (and that may have nothing to do with us, but their own difficulties with life). Sometimes its trailer trash, sometimes not.