Originally Posted by Caysewell
When I was playing, I just thought he doesn't want to play post flop. So any hands he thinks is playable he would just shove pre.
Yes, but you're missing the point. When you have 15 big blinds or less, it isn't worth the risk to play postflop. You don't have enough chips to raise preflop, and then fold postflop. And on top of that, winning the blinds adds a significant portion to your stack (10%).
All of this adds up to mean one thing: If you play a pot with 15 big blinds or less in a sit & go, you should just go all in preflop, even if this means open shoving your stack in.
This is basic sit & go strategy, and is covered in any basic text on No Limit tournaments.
Example 2 (http://www.amazon.com/Harrington-Expert-Strategy-Limit-Tournaments/dp/1880685337)
Now, its not correct to shove every hand when you get to heads up, and there are charts known as Nash Equilibrium Push/Fold charts (yes, Nash Equilibrium is the same guy on the Beautiful Mind movie) that tell you which hands to shove in relation to your stack size. However, the correct all in shoving range is a lot wider than you'd think.
Nash Equilbrium Push/Fold Chart (http://www.holdemresources.net/hr/sngs/hune.html)
So yeah, your shove-happy opponent was probably playing the Sit & Go better than you were, without you realizing it.