When expressing that someone played a role in something, there are a variety of synonyms for the phrase "had a part in". One might say that the person was involved, engaged, implicated, or contributed to the situation or outcome. Alternatively, they may have played a role, taken part, had a hand in, or been a participant in the event. It could also be described that the person was instrumental, influential, or pivotal in the development or execution of the idea or plan. No matter the phrase used, these synonyms convey the idea that someone played a crucial part in the success or failure of a project or action.