Why did my guy coworker suddenly befriend my closest friend instead of me?

Me and this guy coworker who I known longer than my friend that I made not long ago he seems like he be approaching and talking to her know well and also me and him had a misunderstanding and now we aren’t talking to each other at all he moved on to my closest friend?

Why did my guy coworker suddenly befriend my closest friend instead of me?
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