This happened to me also, some details very similar, some diferrent.
We met, he pursued heavily, "loved" me within a month or less, I was his soulmate, the only woman for him, he had been waiting all his life for me.......blah, blah, blah.
Dated for a year, during which time he was the model boyfriend, regularly flying out to see me, running up huge phone bills, lovely thoughtful gifts, always there for me.
I fell in love and started to really believe in him and trusted him without a shadow of a doubt. I relocated also.
We lived together very happily for two and a half years. He proposed. Big engagement fanfare where he told the entire world and his dog that he could not be happier.
Then he left one day with little explanation. For six months I battered my head against the wall looking for answers. He'd meet up with me, got back together with me a few times, told me through tears that he loved me and was just under a lot of stress and needed some time. He subtly made me feel like it was my fault by slipping in parts of me that had "made him do it" (things he'd never once mentioned before when he was busy telling me every day I was perfect) and I set about desperately trying to fix things. He then not-so-subtly set about making everyone around us believe it was my fault too so he got away without looking like a feckless arse.
I was left up shit creek without a paddle in every sense and had to rebuild my life from the ground up.
I wish I could tell you there were warning signs but aside from how quickly and deeply he "fell in love" I could not fault him. Day after day over years he acted and made me believe I was the love of his life and that he could not be happier. He never gave me a moment's doubt and I deeply believed I was lucky.
Eventually a couple of years later he finally admitted he'd not been ready to get married, that he was never over his previous marriage and still held a candle for her. I was a glorified rebound all along. Incidentally he never remarried and remains alone.
The reason I think he was so believable was partly down to his natural character...he was a softly spoken serious sort of a chap not prone to vast displays of emotion and he was well respected as a man of integrity, but moreover because I think he really believed it .
I think when he met me I was a pretty girl, well liked and popular, and he thought he was a fat, bald guy no one would want after his wife left him. He wanted me / became deeply infatuated and I was part of his fantasy. The fantasy where he was happy without his ex wife and I was the real love of his life. He set about becoming my dream man in order to keep me, and unbeknownst to me our relationship was not really "real" if that makes sense.
Fact was, his love for me did not run as deeply as he convinced himself and when he realised that he dealt with it like a coward and ran away, letting me blame and hate myself and not giving me the benefit of an adult conversation to help me to understand what was happening.
He was a very selfish, immature man who gave the appearance of integrity and honesty but he did not possess those qualities when push came to shove. Sometimes it takes a long time to see the dark in someone.
FWIW...my ex tried many times to win me back and I told him to shove up up his arse. He is not, and never was, capable of genuine love for another human being to the level people like you or I are and people like that walk among us undetected.
For as long as they want or need you they will shower you in love, support affection and seeming commitment. They will become what you need. Best friend, protector, selfless lover, devoted life partner and the moment they don't want or need you they are capable of the most unimaginable cruelty to avoid facing the music or seeing the pain they have caused.
Perhaps sociopath? I am not sure. Perhaps. Definitely coward, and most definitely lacking in normal empathy and moral values.
I am sorry this happened to you, but when people treat you like shit you have to try and cling on to the fact that it is their issue and not yours. Some people are well and truly screwed up and not above using other human beings to make themselves feel better. They are not living an authentic life. They are not mature enough for a marriage . I don't think they even know who they are.
I am with someone else now who I love very much. Being with him made me realise quite how inauthentic my ex actually was. I rarely think of my ex, but when I do I admit to feeling a great deal of sadness. Regardless of how things turned out for years I loved this person and the betrayal of that sort leaves a scar on you.
You do come out stronger and wiser though, and believe me, you will be able to smell dog shit a mile off after you're done with this.