Please define "barely". I know you were high during the fight, but I was sober. So it was a 5 rounds fight which Conor won by majority decision. The official scores were 47-47 / 48-47 / 48-47. Not one judge gave the fight to Diaz, it was not a split: it was a majority decision. Do you know the difference? Here, some visual help for you:
Ask anyone who wasn't high as a kite that night: not one of them gave the fight to Diaz. At best, we can say Conor "did not dominate Nate that much". That's the extent where we must stop: it was not competitive and Nate was never close to winning. Conor was outstriking him all night. He did not shoot and Nate did not take the fight down or pulled guard, his "sure" way of victory.
He decided to venture into Conor's territory and got beat up. Re-watch the fight and please don't smoke this time. It's plainly obvious: Conor is the better striker, better cage general and better range manager.
He beats Nate anytime he doesn't panic wrestle. And he won't panic wrestle again: Conor doesn't make mistakes twice.