How to forget someone who changed?

Hi. I have a problem.

5 years ago I fell in love. Deeply. He was my dream. He was kind, respectful, motivated, happy, funny, and very sweet. He was my world and I fell for him badly. He worked a low paying job at a school working with middle school kids and had a simple car and a flip phone and went to a junior college to get his AA degree and transfer.

Then he got married and divorced shortly. And that's hen he really changed. I guess she mistreated him and used him. She didn't work for some time to get her education and once she did it, she dumped him and went off with someone else whom she truly liked. And took everything away too. A really nice car and all that stuff.

Then he moved in with a roommate for some time and during this time he was so quiet and so introverted like he has never been before. I figured that he needs some time. I gave him time.

Then I started learning his behaviors: he began to want to just use women, play around, switched his job to a much higher paying one, quit school, got a Lexus, got a smartphone, ate put at expensive places, moved out on his own, calculated everything... Every penny, and would only spend on himself. Only thinking what's best for him. And I was stunned by that huge change.

Now I out of love. He is no longer in my mind. I hate his disrespect and self centerness.

But I have a problem: I can't stop thinking about the "old" precious person that he used to be. He is on my mind all the time. I tried everything: cutting contact for months, meeting someone else, pursuading myself that he no longer exists, that the young person is dead and was replaced by who he is now. Nothing works. I wanna run to the past and find him. Or run and find someone similar to him now. And I can't. How do I stop these feelings? What do I do?

I do have a busy life of my own and do plenty to keep me occupied but I do thinking about that old person a lot... I told myself 100 yimesthayhes fine and I've accepted that, but can't seem to forget.