If you just cut everything from "Later" in the third-to-last paragraph onward, smart readers would probably still get it but it would be less obvious.
I always find myself confused about the intentions of the joke or the joke teller when they end it in the way you propose. I'd get it, but then be wondering "did the joke teller get it?" or "was there some other punch line that the joke teller intended me to figure out but I didn't?".
It's similar to most of the tests I took in school. I'd spend most of the time figuring out what the teacher intended the answer to be rather than actually learning anything new.
You only have two votes right now, but they counted for -10, so probably 2 strong downvotes. You can see the number of votes by hovering your mouse over the number.
"The dumbest kid in the world"