Khabib Nurmagomedov weighed in on social media, saying ... "Good always defeats evil. Very happy for @DustinPoirier"
"I hope you will get the belt end of the year" ... Eagle wrote.
Floyd Mayweather also took a jab at Conor ... Tweeting a photo of a $50K betting slip, writing, "Thanks for getting me paid!"
The crowd was almost as electric as the fights ... some of the biggest names in Hollywood were in the house -- from President Donald Trump, Justin Bieber, Megan Fox, MGK, Kourtney Kardashian and Travis Barker, Kevin Durant and more showing up for the bout.
KK and TB decided to put on a show as everyone got into fight mode -- straight-up making out as the camera panned to their area.
Cleveland Browns superstars Baker Mayfield, Austin Hooper and David Njoku also showed face ... with the QB sitting right next to UFC legend Chuck Liddell -- but yeah, they did NOT follow in Kourt's footsteps.
#45 made a pretty understated arrival (he wasn't even shown on TV) -- all things considered -- walking into the building to a mix of cheers and boos.