Final answer:
Paul's enemies were able to challenge his apostleship due to his past as a persecutor of Christians, his controversial teachings, his association with Gentiles and lax approach to Jewish customs, and his conflicts with other prominent apostles.
Step-by-step explanation:
Paul's enemies were able to challenge his apostleship for several reasons. One reason was his past as a persecutor of Christians before his conversion, which made some question his sincerity and credibility as an apostle. Additionally, Paul's controversial teachings that deviated from traditional Judaic beliefs also caused dissent among his opponents. His association with Gentiles and his more lax approach to certain Jewish customs, such as circumcision, further fueled opposition to his apostleship. Lastly, his conflicts with other prominent apostles, such as Peter and James, created divisions and skepticism about his authority.