John is impulsive, to the point of being almost random, not as aggressive as he should be to be good at it, but he is bright enough to make losing something that takes some time, rather than being too easy or automatic to be fun.
And it is fun. It's got every bit of his focus, every bit of his attention very quickly. And it stays that way until he's check-mated, at which point he knocks over his own king. "...Rest the board. I'll make tea."