How my ex-fiance lose feelings so quickly?

Long story short we were dating for 3 years, got engaged for 6 months. He is 23 I'm 22. He lives with his parents in their basement and they have an unhealthy family dynamic where the "chord" is still attached and the whole family was down the road. They were all functioning alcoholics. His family and I had nothing in common but I always tried to make them happy but It was a game I could never win, they always found something wrong. Anyway, after our engagement we fought and bickered a lot... but i still love him and he loved me... Tuesday we had a "fight" over his parents because he would want to see them every weekend once we were married and I shut that down. Tuesday he said "etch this is stone I WANT TO MARRY YOU" Thursday we have a huge fight he says he''s not going to break up with me but it became a scary fight that I've never seen before and he said he'd call the cops if I didn't leave and couldn't wait to see them take my a** to jail... He accused me of everything in the book (cheating, etc.) So he ended it after everything we went through... I thought he's come back since he always told me about how much he wanted to be with me but Monday I texted and his response was "I made up my mind, it hurts me too, blah blah blah" and It was so confusing because he always fought for me... I believe his mom had something to do with all of this because she told him, "I'm scared once you marry her she will never let you see me again.." (WHO SAYS THAT?) Anyway, he blocked me on social media or unfriended me but didn't block my number... I don't know I miss him a lot and wish we could work this out... It's been a month since the breakup and I found out he passed his audit exam and so I still cared for him and congratulated him and all he said was "Thanks" it hurts but I don't know what to do, How do you go from one day wanting to marry me to the next ending this all and unfollowing me and basically acting like a stranger? How can I get him back?
Move on he's over you.
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He still is hurting and misses you, but maybe this is his way of coping
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How my ex-fiance lose feelings so quickly?
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