Fedor was just a chubby and short Russian guy in just his third Pride fight
People had seen Fedor's fight with Herring before the Nog fight. He was not just some "chubby and short Russian guy"
At the time there was a bunch of guys from RTT that were in PRIDE, all tough guys, who generally got outclassed by the Brazilians.
Fedor was probably seen as one of those, until he actually started fighting there.
Fedor with his absolute trouncing of Herring by stoppage, a guy who Nog just went the distance with and couldnt finish, was at the very least, a cut above anyone else Nog could fight in PRIDE at the time.
I'm sure Nog was the odds on favorite, and rightfully so, because if he could survive Sapp, conventional wisdom is he should be able to survive anything, but Fedor wasnt some bum coming out of nowhere in this fight. It was for the world title for a reason.
That being said, it was STILL impressive, what he'd done against a elite level fighter like Nog. Flawless victory.