King didn't know the matchup, and Sonic isn't even that advanced a Joker (he is an amazing player). 32 teeth is the ultimate disrespect but he did it constantly because he knew King didn't know shit about how to fight Joker. It wasn't that Sonic used a good character, it's more that he's so much better as a player.
Also, in all 3 of those matches, how often did you see Sonic use Joker's trait? I think he did it once, and it made zero difference in the matches. Even if you don't consider the lack of MU knowledge on King's part, do you honestly think it's right for a character to have a totally useless trait? Something that's so bad that it isn't even worth using? Also, ever ask yourself why he wouldn't use Joker once against most of his opponents and