Can someone help me make sense of my ex's behaviour?

My ex and I separated 9 months ago, I ended the relationship after 18 months, when he kept pressuring me to move in and I was not ready. When I kept explaining I needed time, towards the end he became quite dismissive of me and at times became quite critical of me, so eventually I ended the relationship. Please don't misunderstand, I loved him dearly and we got along very well, I just wasn't ready to move in.

After I ended the relationship, he became very distant (understandable), but he still invited me over for a friend's catch up bbq, at this event he pretended that we were still very much a couple, it was very awkward. He hadn't told anyone that we weren't together.

After this I met with him after about 6 weeks after breaking up at his request, he was cold, distant and quite aggressive towards me. He told me that as I refused to move in with him, he had given up and it was over I hugged him, said goodbye and went strict 'no contact'. I am also off all social media, so he had no way to find out about me. I found out from friends that 3 months later, he had still not told anyone we had separated.

I started to get random text messages from him, 'get well', 'happy Easter', etc; I didn't respond. Suddenly 5 months later he was in contact that he needed to return some clothes to me. Eventually, I directly asked him not to contact me anymore.

Fast forward 9 months later and suddenly I get a 'Happy Birthday' email. He also told me that he was overseas at this family home and had been for 6 weeks. So, he had taken some effort to message me 'Happy Birthday' with the time zone differences, his message was very kind and polite. Our email correspondence continued for about a half hour, and he kept responding immediately, everything was very polite, but distant, although he did say he would pass my love on to his mother.

I then sent: "For what it is worth, 'I miss you'"... Then there was no response and absolutely nothing since.

What the? I'm confused.

Can someone help me make sense of my ex's behaviour?
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