Having a huge stack does not mean you are going to win, far from it! Greg Rayner was chip leader at the end of day two in a live five day tournament and went out on day three, Two crucial hands saw his demise and he lost the lot.
Poker is not absolute Science or Mathematics and many things can and do happen I reached the Final table as the underdog with the smallest stack and with three well timed all-in bets and calls, I reached the heads up position and even then was still the underdog against the other player but I went on to win it.
Luck or skill? I can argue for both reason's, but I always say "the game ain't over until the fat lady sings" and anything can happen.
Having the biggest stack only means you have the most to lose, so you still have to be careful with how you play, because the underdog will always make moves that will shock you, He is in the position that if he doesn't double up against you, he is definitely going to lose, so he has to be ultra aggressive and play hands that are marginally better than yours and hope to double up.
It doesn't always happen but If I am up against a stack that is 3 or 4 times bigger than mine I am happy to finish in second place and will shove regardless of what cards I am holding Ace Rag, or any Pocket Pair, Suited Connectors, even one gap connectors they all have a chance and yes I am relying on Lady Luck! to come knocking at my door, but doesn't Luck always play a part when playing Poker?
That is what makes the game so much Fun!
When the fun Stops, STOP!