Why would a guy reject you and then keep tabs on you on social media every day?

Anonymous
Happened to me. Got rejected by a guy 8 months ago and ever since I stopped following him on social media (as it was too hard for me to remain friends) he keeps tabs on me online everyday (especially when I post an instagram story and we aren't following each other).
Why would a guy reject you and then keep tabs on you on social media every day?
3 Opinion