Stylistically he matches up well. Has long range boxing, good take down defense, good off his back. I don't think it's crazy at all. Khabib hasn't fought enough guys to say that he could just beat anyone willy nilly.
Could Khabib do what GSP did in the 2nd fight against Penn? It's possible, but it's worth noting GSP and Khabib have totally different strengths athletically speaking and GSP is bigger.
Khabib has had one title defense as the undisputed champ (and he really his title was still disputed...because Furgeson had claim but I digress) and people think he's the GOAT lw? I don't understand MMA fans really.