Although learner interactions in forums are well-documented, research on instructor engagement strategies in MOOC forums and their impact on forum dynamics is limited. This study offers a distinctive approach by categorizing instructor strategies into four types: communicative, integrative, task-oriented, and non-interventionist. Six prominent courses were analyzed using social network analysis, machine learning, and quantitative methods. Findings show that the communicative strategy enhances knowledge transfer and network robustness. Task-oriented and integrative strategies promote frequent interactions but are linked to higher plagiarism rates. The non-interventionist strategy reduces forum activity. Except for task-oriented strategies, active learner participation is positively correlated with the number of responses to initial posts. Based on these findings, the study offers recommendations to enhance teaching and learning practices in MOOCs.