I don't understand Corki

Corki is well known taboo in ranked games (at least at silver). If you pick or ban him it is likely that no less than four of your teammates will report you/ dodge the game. But last night in the World Championships there was a Corki ban. I assume the people competing for the title of the best LoL players in the world know better than Silver players, so what's going on? Is Corki a legitimate pick? Was he always a legitimate pick? Or did he recently get buffed or something?