if we are to believe that YX went and had his time travel adventure (DDD & and KHIII) and THEN returned to dark road I think it gets kind of weird yes, return to your time travel origin erases your memories but your experiences are "etched" in your heart (basically inception) so even before starting DR this was a Xehanort already drawn to darkness, I find it hard seeing him form a relationship with Eraqus and the other students, or being really affected by what happens to them but the other way around makes more sense, DR being a naive Keyblade student who's experiences trying to rescue the upperclassmen leave him traumatized about how weak people can be easily taken over by darkness, thus he decides to leave Scala after talking with Eraqus and meets Ansem again, now more interested in his plan for gaining true power and controlling the darkness and thus, in order to avoid future debates about his hair he decides to go bald