Trying to understand the OW, H etc, seems pretty normal. What you'll learn over time is that while you enjoy a good puzzle, some things you cannot understand. You don't have the information or mind set to understand those things. But trying after a 20yr relationship is pretty normal.
Mine did the same things. Found somebody broken (he may not have been as broken, but she was willing to help in that regard as well )and tried to fix him. I remember commenting on how interesting and fascinating it was. During the process of her leaving I said that many times becuase while it was painful, it was not lost on me how interesting it really was to see her leave and then try to justify. Where truth wouldn't support it, she made things up. Where the OP wasn't quite broken enough, she made that happen as well. When I wouldn't play along in the part she cast me in, she changed tactics. She lied and pushed and shoved and... Anyway, it seems normal and I kept asking "why" for a long time. In the end, I realized it makes no difference. I ask "why" sometimes anyway, but the answer is always the same... it just is and "why" is irrelevant.
I am relevant. My feelings are relevant. My perspective and my ability to forgive as I have been forgiven, time and again is what is relevant. Forgiving is not the same as not having boundaries. It is not the weak stance, in case you wondered. It is far harder to forgive over and over and over again vs. becoming angry and looking for vengence and justice. It is hard, but you need to work on that way more than understanding "why". You will spend your time much more wisely on forgiveness and yourself than on figuring out "why" IMHO.
I tried. I heard others say it. I tried anyway. I know now they were right. I knew then they might be wrong, but I was the one who was wrong.
Spend the time wisely. Live like you mean it. Live without fear and you'll do very well. Fear is not needed in this case.
You are a wonderful person even if you cannot see how things will unfold. Stop worrying about tomorrow and let go. Focus on you and on letting actions speak.
AJ
"Our lives begin to end the day we become silent about things that matter" MLK Put the glass down... "Yesterday I was clever so I wanted to change the world Today I am wise, so I am changing myself."