Why did my ex call me?

My ex boyfriend of 6 years broke up with me because he met a girl 5 years older than him. They got married in 5 months, although he called me telling me that he wasn't too sure, I guess trying to hint for me to try and stop him. A couple of weeks ago, one of our close friends was killed, and we just needed to talk to each other. Just talking about death, nothing more, she found out that we had been talking and hit him in the face. He called me crying and I got a mean text from him mom telling me to respect their marriage. Although it was a bit unfair, I decided to keep my mouth shut. Well, my birthday was 4 days ago and he called me at 3 in the morning, just to wish me a happy birthday. He tried to hold a conversation but I shocked at what had happened. Why would he call and say happy birthday whenever he's married and last time we spoke, everything blew out of proportion?
Why did my ex call me?
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