ELI5 Olympics - why the amateur vs professional line blurred?

Why were the Olympics so strict about amateurism in the first place? Why were professionals not allowed initially? Who was disqualified for being a professional? How did the lines between amateur and professional blur? Are there any sports left in the Olympics that still maintain that strict amateur status? ... we explain like I'm five To the ELI5 community that has supported us so far, thanks for all your feedback and comments. Send us an e-mail: [email protected]