Why would a guy try to make a girl jealous intentionally?

To make a very long story short, I thought this guy was interested in me (he showed signs) so I decided to make the first move and talk to him. We hung out twice, and we ended hooking up. After that he ghosted for a few weeks, then all of a sudden started talking to me again. So I told him that I wasn’t interested in a hookup, and he told me that he didn’t know what he wanted, but wouldn’t mind getting to know me better. Anyway, we never talked after that. When the semester started, he would literally avoid me in person, but he added me on social media. Fast forward to this semester, I’ve blocked him on all of my social media, and I’m trying my best move on, but he’ll get in my proximity, and flirt with other girls. As if being ghosted after hooking up with a guy isn’t hurtful enough. It’s kind of like him nonverbally saying, “you weren’t good enough, but this girl is.” I know he’s intentionally doing this because he smirks when he does it around me. To be honest, it hurts and it makes me feel of a lesser value. What do I do?
Why would a guy try to make a girl jealous intentionally?
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