It's the misdirection. The listener is expecting the whole time to find out why this guy chose these wishes and in the end it turns out he's just an idiot.
Reminded me a bit of the old joke about the guy who's dating a girl and is meeting he parents for the first time. He's sitting in their living room talking to his new girlfriend's mother and father and their family dog is sitting under his chair. Things are going swimmingly when he feels some gas building up. Suddenly, a small fart squeaks out and the guy is mortified. He's about to apologize when the father says : "Oh Spike! Get in the kitchen!" The dog sheepishly lumbers off and the guy can't believe his luck. A few minutes later, the dog comes back out and sits under his chair again. The guy is still bloated and lets another fart slip, this one a little bigger. The father yells :" Spike! Damn it, I thought I told you to get in the kitchen!" and the dog takes off again.
A few minutes later, his gas is getting really bad and the guy is about to excuse himself to head to the bathroom when lo and behold, Spike returns and sits right under the guy's chair yet again. The guy figures he'll make amends with the dog later and lets a real rip go. He's finally feeling better when the girl's father jumps up and shouts : "SPIKE, GET BACK IN THE KITCHEN BEFORE THIS GUY SH*TS ON YOU!"