Take any number of fighters with the same reach as Nate at 145 or 155. Now, subject them to the shots that NATE TOOK in the first fight and how many go down, or are finished as a result? I'd say a majority of them at least go down. Nate's ability to absorb punishment was more of a factor in that fight than his reach.
First off, I gotta just come back to the notion that Conor simply gassed. I said it before, but you just brushed past it...
Conor's cardio didn't magically disappear while undertaking an
easier cut than usual (he basically wasn't even cutting anything). He gassed because he was not controlling the pace. He gassed because Nate was landing lots of shots. Nate was landing said shots because Conor was for once, not at a reach advantage. Toss on top of that fact, Conor was not able to work his normal angles against a fellow southpaw. Some of his best offense was simply negated by not facing a righty.
Take any number of fighters at 145 with a 77" reach? What? There don't appear to be any. That's what I apparently failed to drive home to you last time. Not one fighter Conor fought at 145 had a reach advantage. Not one. How is this possible? He has long arms for his frame, and a remarkable ability to cut weight. So yea, when you're literally bigger than everyone you fight... you kinda have an advantage.
As for guys at 155 that have Nate's reach or greater? You'll be hard pressed to find many. Kevin Lee and Ferguson are the only guys right now with comparable reach. So you have literally no 145ers, and just two at 155 that occupy spots in the Top 15. He literally has a reach advantage in almost every fight possible, save Nate, Lee, and Tony.
Now onto the notion that he lost because Nate is just super duper tough, and that's the reason why Conor had such difficulty. You're operating under the pretense that Conor was able to land his best strikes, in that fight. No. He did not. Nate is tough as hell, but he's not super human. Conor was not teeing off at will and just crushing his own gas tank trying to slow the unstoppable juggernaut that is Nate Diaz.
Nate's striking, and reach threw Conor off his game. He only landed a few nice shots, with none of them being devastating fight-ending blows. Again, the reason why he couldn't land the same brutal shots he is known for is obvious - He has to be in range to do so. He had trouble getting to Nate's chin, not because Nate's hard to hit, or because he's durable. He had trouble because for once, Conor was facing a man with longer arms. It's really that simple.
And this all goes back to the very basic premise that is Fighting 101 - Size matters. I know this is a hard pill to swallow, but a LOT of Conor's success us based upon just being big at 145 (which is of course predicated upon his abnormal cutting ability), instead of him being some uber GOAT contender.