All the talk about body language, staredowns etc. in MMA and constant claims of both fighters being shook in the time leading up to a fight is generally BS. It's stuff people write to hype up their favorite or try and take away from the credibility of a fighter they dislike.
That being said, comparing Conor McGregor's usual approach to carrying himself during walkouts and staredowns to this one particular fight with Khabib, he does indeed look much less brash, there's less showmanship, and even the billionaire's walk after entering the cage looked like he only did it cause it's part of his iconic entrance, not cause he was in the zone the way he seemed to be when he did it before fighting Alvarez. For some reason, his whole appearance was much more intense at the weigh-in ceremony than it was when they were in the cage that night. Now for why that was, I won't make any interpretations, all I can say is that McGregor looked different here than he did in all his other fights.