Fascinating...Why after so long?

So, Two days ago....I am talking to my Friend Elena, on skype. Then my phone Vibrates. Not reckognizing the number, I quickly opened the message, to see who it was from. I was Astounded. I could Not believe it, Dave....The man whom I almost ruined my marriage with. If it wasn't hard enough to see his name in that message, he went on to apologize. That apology, I believe meant more to me, than any apology I had Ever received. It had been 5 Months since we last spoke. After receiving the message...I called him. Maybe not a good idea. But I had to know...why now?? Why after so long, did it matter? And this is what he said, " I have lost a dear friend recently, and on my way home, the second person to pop into my head was you, and how I had done you wrong." I was floored. Never in a million years would I have guessed this. We continued chatting for a while. It was as if Nothing had ever happened between us. It wasn't akward at all. In fact we had an amazing time. We laughed, until we couldn't laugh anymore. We talked about the things that had happened in our lives since the day we stopped talking. I told him Thank you....as he kind of chuckled under his breath. I said," I know it may sound odd, But you saved my marriage." I to this day believe, had it not been for what happened between us, my Husband and I would have Never been forced to discuss issues that we had never dared to cross before. I know it must sound strange. But at this stage in my Marriage, things had very quickly gone from Amazing to nothing short of Awful. I couldn't handle it anymore. So Yes...I Thanked Him. At this time, I feel as though we can Be friends again. He was one of my good friends, and that's just something I'm not willing to compromise on. I discussed this with my husband, as I have No reason to hide anything. He understands where I am coming from. He says,"I trust you" which is amazing to me. I have Not heard those words in quite sometime. I believe that in these past few days, our adventure together has just begun. So My question to you is.... WHY?? Why after so Long, did it matter to him?