Why would a guy stare, want my attention and tell his friends about me if he was not that into me?

We both go to college and are in the same major. He used to like me way back but his interest subsided since we didn't have any contact. Years later he hears rumors that I’m into him and starts turning around and staring at me again to get my attention, always keeping an eye on me and telling his friends to watch me too and acting visibly nervous. Once he would follow me to the subway station and watch me from afar from the other side. He did this for about a year until he finally stopped (maybe he got into a relationship I don't know).

Since we are both soon graduating I wanted to know why he stared at me so I messaged him on WhatsApp where we made friendly small talk in the beginning. at first he pretended he wouldn’t remember me which was probably a lie but he still remained friendly. Then I asked him if he wanted to talk to me since he was staring quite a bit and why he didn’t approach me. He turned very cold and said „I guess I was never that interested“ which is a lie since everyone knew that he had a crush on me at some point. I told him that I was too shy to approach him myself. If he is over me, why would he be so insensitive and deny he ever had any interest in me? He could have just replied more neutrally saying something along the lines of „I didn’t know how“ etc. But he chose to lie about his interest in me and be very blunt. I was not acting pushy during our conversation, I just wanted to clear the air and say bye since we would never see each other again.

Why would a guy stare, want my attention and tell his friends about me if he was not that into me?
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