I know we haven't finished the film yet, but you clearly understand now that Ernesto "Che" Guevara returned from his motorcycle trip with a new attitude towards the poor. It is important to remember that Che sacrificed a life of privilege in order to wage his revolution.
So, what changes a person? Have you ever had something happen to you that dramatically changed your outlook on life? If so, what was it? If you are not comfortable talking about yourself, then theorize about what changed Che in the film.