Everyone is trashing Zook for going for it, it fits the meme that he's a terrible game coach. I actually think it's complicated and he could have been right.
First off, the success rate on 4th and 2 is pretty good, around 60%. If they made it they have a much better chance of getting the TD than they would from the onsides kick, being on the 10 instead of the 50.
Finally if they kick the FG from the 12, they are leaving the best-case scenario as overtime. If they get the first down and then the TD, they still have a chance to make a TD after the onsides kick and win in regulation.
So there are factors going both ways, I can't kill him for going against coach-think in that position. On the other hand I didn't like the play- I'd probably have had Scheelhaase run if I absolutely needed 2.