Why did my ex-crush unfollow and remove me on instagram?

He unfollowed most of the girls in our university when he started to post about his girlfriend. This guy is a known flirt. But he only removed me from following him. Most of the girls had to unfollow him manually when they found out that they have been unfollowed by him. After unfollowing majority of the girls in our university and removing me, he changed his username so I did not get to know that I have been removed. I found this later on when my friend, who was also unfollowed but not removed, unfollowed him back and told me about it. Can you tell me why would he do that? Also, when we were in offline classes, he used to stare at me. A lot. Even my friends began to notice it. So I started to catch him whenever he started to stare at me which caused him to stop eventually. Has this got anything to do with what happened?
Why did my ex-crush unfollow and remove me on instagram?
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