Why would a guy who unblocked a girl 2 years ago randomly unblock her and then friend her 3 weeks after that?

So people we worked with said he was obsessed with me but he blocked me when I got drinks with a few of our coworkers. I knew he was talking about me a lot, especially to guys I would talk to, and it would be a mixture of me being brought up randomly in the conversation to negative things. We talked in person a year ago after a year of not seeing each other and I told him I couldn't keep playing games and that I deserved better and he started crying. That was the last time I saw him and then 2 months later he started dating a girl who hated me. Then she cheated on him and a few weeks after he started having other people message me to see how I was doing. That went on for a few months and then 3 weeks ago he unblocked me on Facebook (not the other social media platforms). Then he added me as a friend 2 days ago. I'm very confused as to why this is happening but I dont want to reach out.

Why would a guy who unblocked a girl 2 years ago randomly unblock her and then friend her 3 weeks after that?
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