The sculpture was packed separately from its base to protect it during shipment, and so arrived at the academy in two parts - the laughing head and the plinth (the support where the head rests). The judging panel assumed the two pieces were separate submissions and decided the support was better.
You can judge for yourself. The images below show the original sculpture, and the plinth as it was displayed at the Academy, complete with the little piece of wood that would supposedly hold the real sculpture.
As with most things in the art world, aesthetics, reason, and common sense are as important as having a parachute on the Titanic. It’s a bit like drawing masterful pieces that aren’t worth shit, and then selling ugly distorted paintings for obscene amounts of money. No, wait a minute! I think that one is called Picasso.