Consider recursion - Adding numbers.
It appears that the vast number of upvotes on a humorous answer push up the delete threshold on this vastly downvoted question.
Is this really quite the intended effect?
Preserving an incredibly good (and thus, highly upvoted) answer in spite of a terrible question (highly downvoted) question, that is an intention of the system. The reason it is based on both question and answer votes was because of an initial concern users had that excellent answers were being destroyed thanks to awful questions that they happened to be posted on (the turning point being a couple Eric Lippert answers).
So in that vein, something that's so terribly voted down, that has an answer which is so vastly upvoted, that's technically an intended effect that it is more difficult to destroy.
In this specific case, though, it's more of an anomaly because the votes here are an anomaly. As noted by balpha in a comment, it's a Proggit link, which explains why the votes are much higher than the answer may truly be useful for.