Montag was never truly passionate about his job, but he did just want to do it as a firefighter. But once he saw the lady who loved her books, he started switching opinions on books, his job and society. The audience knows this because of his inner thoughts he is having during the events and after them. Many people do that today, they have a job they don't have passion for but like it because they are getting paid because of it, so they don't really mind it
