When an opportunity is created in Marketing Cloud Account Engagement from the sync with Salesforce, the campaign that is set on the opportunity is the first campaign of the first contact associated with the opportunity. This means that Marketing Cloud Account Engagement will look at the contact roles of the opportunity in Salesforce, and find the contact that was added first. Then, Marketing Cloud Account Engagement will look at the campaign history of that contact, and find the campaign that was assigned first. That campaign will be the one that is associated with the opportunity in Marketing Cloud Account Engagement. This helps Marketing Cloud Account Engagement track the source and influence of the opportunity. For more details —> 678