When I first watched Chamber of Secrets, I didn’t understand that Tom Riddle literally was Voldemort as a teen. I guess I thought of Voldemort as an evil spirit or being that never really had a childhood. I thought that Riddle was merely a supporter of his who had let himself be possessed like Quirrell had. When I started reading GoF a couple years later, I thought the ‘Tom Riddle’ who was killed had been the same Tom Riddle of CoS, killed by Voldemort once he no longer had any use for him. Eventually I realized the truth.