Your impression of people are mercurial.
It depends on the how you met, when you met, your mental state, their mental state. It depends on events that took place subsequently, how each event went, who were present there how influential they are to you and to the people around you. Then there is how close you are to each of them, and how that changes with time. There is also how often you meet, what kind of interactions you have. You can also bring your own mental makeup into the picture.
Now mix all these together, in no particular order, and in no particular quantity. Then you may get the reason for the particular impression. You may also get the impression that there is no reason at all. You could also trace the impression change with time, or any other aforementioned variable.
Impressions. They are not state functions.