The ultimate cause of what's happened has been the advertising campaign.事情发生的根本原因在于那场广告宣传活动。Lack of money is the ultimate cause of our problems.缺少资金是引发我们问题的根本原因。The ultimate cause of what's happened seems to have been the advertising campaign.出事的最根本原因似乎在于那场广告宣传活动。