I think the joke is that in all cases but the best-case, you won't be around to observe it, this becomes practical once you can create a universe for every perm

I think the joke is that in all cases but the best-case, you won't be around to observe it, this becomes practical once you can create a universe for every permutation and destroy all but the universe which notifies you that it's the best-case. In all good text books this is left as an exercise for the reader.