@seekingwolf, for a number of reasons.
First, new environment, having to make new friends, living in space that’s not familiar.
Second, being responsible for yourself in new ways. While not having your parents around is a good thing, it’s also difficult, because you are responsible in new ways.
Third, college level work is work. Not matter how well prepared you are coming into college, there is a big unknown factor about university level work. You have to deliver.
Fourth, no matter what your social status was in high school, the pond is bigger, with new competition.
The good news is, when you return after the holidays, the situation is no longer new. You know how to find things, what’s good in the cafeteria, where the study spots are, how to get an appointment with an advisor, etc., what the drama factor is in the dorm, where to meet people. It really does get easier. You will begin to see people in class that you recognize from first semester, and that alone will be a reason to speak to them. Making friends gets easier.