Why is he mad at me for moving on?

So this guy and I were talking a lot over last Christmas. I decided to tell him I was into him and he said he was into me as well but he was getting a girlfriend but he wanted me to stay available. It really broke me that he could be so douchy and I decided to move on.
In the time we were apart, I focused on myself, I made a lot of new friends, I hung out with a bunch of guys, got a boyfriend. Now he’s started talking to me again, but I’m pretty sure he still has a girlfriend. It’s like as soon as he saw me doing well without him, he got mad at me.
He’s extremely rude to me everytime we talk. When I refused to send pictures he told me I’d never be enough for him anyway. He said he’s not happy with his current girl, and I told him that’s not my problem. Why is he mad at me because I’m doing better without him? And if he wants me back like he says he does, why does he treat me like shit?
Why is he mad at me for moving on?
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