The growing dissemination of conspiracy theories on social media has challenged the well-being of societies. This study aims to understand why individuals would engage with conspiracy theories and what role specific beliefs, but also individual factors such as personality traits play. To answer these questions, we conducted surveys in six countries (Belgium, Switzerland, Germany, France, the UK and the U.S.) and investigate three motivations (conviction, entertainment and reaction provocation) behind the dissemination of conspiracy content on social media. Our findings demonstrate that across issues, individuals who indicated they would engage with conspiracy theories do it mainly because they are convinced by the message. Political orientation and issue attitudes proof to be connected to individual engagement with conspiracy theories out of conviction, while dark personality traits such as narcissism and psychopathy are valid predictors for why individuals would disseminate conspiracy theories out of entertainment reasons or to provoke reactions.