I wouldn't claim randomness. But I don't think there is a playoff mismatch that is ever really much more than say a 57-43 edge. That edge is substantial, but not so much where upsets don't happen all the freakin' time. I mean you break down Atlanta - they lost a bunch. But you look at say the 1991 World Series (still probably the most dramatic World Series of my lifetime), every game but one (an Atlanta win) was a coinflip.
I just look at baseball - with the oversized importance of pitching, and how teams rotate starters. It is rare that any team is rolling out a demonstrably inferior squad every single game. Put another way, the 1972 Phillies were not a sorry team on Steve Carlton days.