Brock Lesnar in 2008 arguably brought the UFC to new levels of exposure, and did the biggest numbers the business had ever scene at the time. Before Brock came to the UFC in 2008, the UFC as a whole didn't feel as complete for some reason. Conor in 2015/2016 was breaking viewership records, and was getting notoriety in not just the sports media (ESPN,Fox Sports) but in mainstream media as a whole. But we could also say Rousey's popularity helped Conor to, with so many eyes on the UFC during her reign of terror. You could also argue TUF in 2005 brought the UFC to mainstream sports media to.