When you have an idealized picture of someone they would never live up to your expectation of them. The fact he ended his relationship and then tried to break you up right before your marriage is a huge flag that you seemed to have overlooked you have spent the years since with the pain of doubt which he intentionally inflicted on you. I bet he didn’t break up with his girlfriend because of you, his timing is manipulative to say the least. He broke up probably because he was a shitty boyfriend and decided to chance his arm with you because he felt lonely. These are things you never considered you just allowed his actions to disrespect your relationship and instead you think he is wonderful.