Cause all he has showcased thus far are decent striking, mediocre grappling and outrageous luck. Holloway was only 21 at the time, Brandao and Poirier are journeymen, Brimage and Siver should be fighting in the women's trawweight division, Mendes took the fight on 2 weeks notice and Aldo made a huge mistake and basically KOed himself. McGregor should have lost his last 2 fights given his limited skillset and will most likely lose to all the top fighters at featherweight and lightweight unless he gets lucky again. I would even favor mid-tier fighters like Doo Ho Choi or Joseph Duffy over him. McGregor will have to beat RDA in decisive fashion to prove he's really legit.