Khabib didn't just beat him, he fucked with his head the whole time he was doing it. It's more or less the turning point beyond which he was redeemable - after this fighting was over - he wasn't gonna be the champ ever again because he was leagues behind Khabib, PR, Cocaineyness, being a pain in the hole and a bully went full time from here on - before this they were side projects to retaining belts. TLDR it's raging bull, except with money.
I reckon in his own mind he thought he did okay in the Khabib fight. It was the two losses to Dustin Poirier that proved he was done. Annoyingly, at the beginning of his career he seemed alright. A bit of a Dublin mouth, but appeared to be an actual martial artist in his ambition, skills and movement. The moment i was sure he was 100% cunt is when he punched Nate Diaz in the hand in the run up to their second fight.