Casillas spent half his career being a liability nobody could ever tell me he's better than Buffon. His name value is what won him so many awards. Real managers had been wanting to drop him since Capello in 2006 and it only took another 6 or so years but Mourinho did it, Ancelotti continued and then he was finally let him go.
And for those questioning Buffon's inclusion it's more the quality of his performances. He broke the Serie A record for consecutive clean sheets, was influential in Italy's surprising run in the Euros (beat Belgium, Spain and lost a close tie to Germany on penalties), won the Serie A, Coppa Italia and continues to be influential. His performance again Lyon in the CL group stages was a great individual goalkeeping performance.
And he certainly deserved it last year, when it was shockingly given to Neuer ahead of him so if anybody does feel like Buffon doesn't deserve it it's a good case of the award levelling itself out.