Why would he be interested in me all of a sudden?

So there's this one guy who never said anything to me and walked by me avoiding eye contact. He never really talked to me and didn't seem interested. I saw him talk to a few other girls but i was almost invisible to him. Now he's all over me and is always looking for me. He's super jealous when i talk to guys but before he didn't care at all. Why is he so possessive and interested all of sudden?
Why would he be interested in me all of a sudden?
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