Why does he keep coming around?

I dated this guy for a few months, then he dumped me to go back to his x. I Haven't texted or called him since that day at all. I don't want to intrude on a another woman space nor disrespect his decision. However, he constantly shows up where I work, rides by my house, and talks with my friends. I thought it was just me noticing these events, but now my coworkers do as well. I just don't understand why he keeps doing these things when he was the one that dumped me not the other way around. Some advice and insight please