Why did he do this?

My ex found out that I went to a dinner party that a guy asked me out on. Around the same time he posted on Facebook "I had lived through the same story before,and I know how it'll end. I guess I'm, and should be, glad that's the ending . Everyone's wish comes true. Win-f******-win". He was the one who asked for the break up and afterwards complained that I was still to attached, so I moved on. Later he asked how it went and I told him we enjoyed ourselves and that he made me happy, he replied "Happy to hear that :)"