How did people know Britney Spears lip sync?

People speculated that Britney Spears lip-synced during performances due to her highly choreographed dance routines, which made it difficult to sing live while executing such complex moves. Additionally, during some live performances, audio discrepancies were noted, where her singing seemed out of sync with her lip movements. Fans and critics also pointed to instances where her vocals were noticeably consistent, leading to doubts about her singing live. These factors contributed to the widespread belief that she often used pre-recorded vocals in her shows.