Social media rumors often originate from accounts with a low number of followers, yet these rumors can surpass the spread of genuine information disseminated by opinion leaders. This counterintuitive phenomenon is indicative of the complexity of rumor propagation, which we refer to as the power of marginality. In this study, an agent-based modeling approach was employed to examine the disparity in the impact of rumor propagation between marginality and opinion leaders. The findings reveal that while the overall influence of opinion leaders is substantial, it has a discernible upper limit. Marginality, on the other hand, can exert greater influence on a larger number of users with fewer connections, and this attribute grows gradually over time, illustrating a more stable influence dynamic. Additionally, the dissemination of rumors by opinion leaders accelerates the fragmentation of group opinions and increases the number of echo chambers within the network compared to marginality. These results underscore the need to avoid overestimating the capacity of opinion leaders to disseminate information and to pay attention to any social media users engaging in rumormongering. Methodologically, this study employs research techniques that can analyze complex systems and provide recommendations for future research on rumor propagation.