He got it because he reported the exploit in TF2 where any player could get any item they wanted. Valve was so grateful, they basically said "You name the item, we'll give it to you." I'd have got something maybe like a strange B.M.O.C., effect: vivid plasma (or maybe blizz. storm for the Christmas theme) painted purple, craft #1, level 9001, gifted by GabeN himself.
Once you are actually offered the ability to have any hat in the game with any effect you realise that you don't actually care about theming, and would rather have a nice looking hat with a cool effect.