Ok so here's the situation. I just moved to a new building not far from my former workplace. So every time I'm having my break, I always bump to my former coworkers. Some of them say "hi" to me but most of them try to avoid me as much as possible or they pretend they didn't see me and avoid eye contact. It's strange because my former managers are still very nice to me. I wonder why?

Because you got away and they didn't. I'm not joking.

Why would they like to leave that place? It seems like a good place to me to work at. In fact, I really felt sad when I left it. So I don't know why they avoid me like that. I was thinking more of like they don't want me back there.

You're over-thinking it. People typically are thinking of themselves when they mistreat or snub others.

What I mean is... just like you're here in this forum trying to figure out how their behavior relates to you, how it might be your fault, how it might really be about you, I promise that most people are doing the same thing.

If they mistreat you it's because in some way you make them feel bad... no, strike that... because when they see you they feel bad/uncomfortable and then punish you for the way they feel.

This is so typical and common playground behavior. People want it to be someone else's fault that things aren't the way they want...

Anyway, as I said, the way they treat you is a reflection of their problems, not yours. Don't fret it or they will succeed in their unconscious quest to make you feel bad because they do, for whatever reason.

Ok so here's the situation. I just moved to a new building not far from my former workplace. So everytime I'm having my break, I always bump to my former coworkers. Some of them say "hi" to me but most of them try to avoid me as much as possible or they pretend they didn't see me and avoid eye contact. It's strange because my former managers are still very nice to me. I wonder why?

They may simply have social anxiety and avoid communication, or it maybe because they are jealous.. But if they avoid eye contact it shows something... For you I would suggest to forget about those who don't want to communicate, nice person would want and if they don't -they are not nice. And you don't want to talk to people who are not nice;). Stay in touch with those only who respond to you.