Why are my coworkers starting to show their true colors?

When I start to work there everybody seems happy like they they seem nice now its been a month my coworkers are starting to show their true colors some will talk behind your back, then there's this person (Nik) who will always report your smallest little mistake to your boss every time you make a mistake, Others you can't even ask one question and they will get mad at you for interrupting them, Some are extremely rude Plus I feel like some of them are fake but Im confused most of them are very nice when I first got there. But one thing I noticed there they tend to favor the people who have higher rankings in our job like boss or person higher than them. They treat them nicely they are not even rude to them but they very rude to lower rankings than them like me. Just my observation they treat them differently than regular employees. So now I dont ask questions anymore I dont interact with them anymore I just talk when ask but I dont engage in their gossips. I also thank God most of them are not my friends on social media and I dont plan to add them in the future for my peace of mind.
Why are my coworkers starting to show their true colors?
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