I would say you are the exception if you are the same person you were twenty years ago. Most people have changed dramatically whether it be for better or worse. Some have changed religions, realized their sexuality, developed different political beliefs, etc. What makes xavier an extreme case in why he has changed is moira and the fact he was able to absorb the knowledge of her past lives. This would shake anyone to their core and make them second guess every pre-conception they ever had. Not only that, in forming krakoa, he has had to modify his dream to encompass all mutants, instead of a select few who will just blindly follow him. Even before hickman, if you stick with just the 80’s and the claremont era, xavier goes through radical shifts in paradigm. All of the xmen do. This is just how people are. We grow or we regress but we rarely stay the same. Time moves forward and our experiences changes us for better or worse.