If you're the COO, and most of your compensation is in stock or bonuses related to the stock price, and the stock nearly triples during your reign (15.92 to 41.07)... you're going to get a big payout.

I also don't really buy that firing him cost this much, since much of it seems to have been a sunk cost. That stock was going to vest eventually whether he was fired or not, it just vested faster because he was fired.