The USADA testing took down Cro-Cop, Belfort, Overeem and others, but whether they fought clean or not, Fedor in his prime would beat Stipe badly.
And Feder wasn't juiced. Just a stoic, grim, Russian warrior.
I remember Randy Couture commenting on Feder's unemotional, stoic, almost detached demeanor; saying that when you look just at Fedor's facial expression (or lack thereof) as he walks towards the cage you couldn't tell if he was going to the biggest fight of his life or going to get a haircut (which is even more funny since Fedor was bald).
It just goes to show that you don't have to be a loud mouth or act like a clown to be popular, fill the seats, and have a loyal following. Just win.