Guy's Behavior

Coworker suddenly nice to me. Do I need to watch my back?

A coworker stopped liking me for some reason about a year ago and turned the other two coworkers we worked with against me. They had their own alliance, singled me out and pretty much had their head up his ass and took up for him. One of them was our manager. He is now the manager in the department and is being super friendly to me. The manager got demoted to a regular employee. I was alone and singled out while they had their own group but since then we have hired new coworkers who I can hang out with and the guy is the manager. He has been doing things for me that he doesn't have to do. He never apologized but he told me that he didn't want me to feel singled out and not apart of the team.
Coworker suddenly nice to me. Do I need to watch my back?
Post Opinion