If anyone's interested (though this is mostly just for myself), I'm making this to discuss the differences between the early versions of King of Cards and the finished game, as it went through quite a lot of changes (probably the most) which no one seems to be talking about (yet).
First off, the plot. Early info made it seem like King Knight really did plan on usurping the 3 Kings and Joustus/becoming the King of Cards is just a side goal. In fact, he didn't even know about it until somewhere early in the story (although he already somehow has his own deck of cards. Maybe he thought the cards were pretty and just randomly decided to pick them up?). In the game's proper, it's revealed that King Knight really only wanted to win the Joustus tournament. Sure, he obviously still wants to be a king, but there's no plan of usurping anyone. His actual plan is just: "Step 1: Win the tournament and gain the title of a king. Step 2: Get vast riches. Step 3: Build own kingdom (how????). Step 4: Success!" Now, of course, we know the Enchantress will dip her hand into this and King Knight will eventually usurp the throne, but I'm pretty sure that wasn't his original intention.