Why does my ex draw things related to me ?

I left my ex 5 years ago for many reasons.
He's an artist, he usually post on his instagram his drawings. At the time, I found out that he had an account on a Japanese forum that he didn't share to his friends, he puts his drawings in there too (including some drawings of naked girls).
After break up, I noticed that he started to draw things related to me. For example, my favourite color, drinks, my hobbies, .. I know that he thinks I found out about these drawings. He keeps stalkings my social media profiles and then returns drawings things he found out about me.
Why does he do that ? even if he doesn't text me, he talks about what I'm doing (my work and hobbies) to his friends and new girlfriend so that they do the same (without mentioning that it's actually WHAT I'M DOING). He's mirroring me and it's annoying. I don't want to talk to him about it, I don't want him to know that I'm stalking him and thinking about him again.
I just want to know what's his purpose of doing that ? Does he want me to come back ? Is he obssessed with me, or does he do it to get my attention ?
I deleted my social media accounts recently. Few days after, he set his instagram account to private (he did quite the same so that I don't stalk him).