Why do guys come back around when they can see you’re with someone?

Context: this dude would go hard and ghost me for months at a time until I put a stop to it and told him I didn’t want any further communication with him. It used to go on for almost 2 years and he’d promise all these things to me but never delivered just would pop in and out. Now I’m happy in my relationship I post about it all the time, I love my man and then last night this dude literally messages “Hey” like I’m going to respond. A lot of balls on his part. I’m just wondering if I was dealing with someone who was mentally deranged or something.

Why do guys come back around when they can see you’re with someone?
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