The question was closed as it does not qualify as Purim Torah under the Purim Torah policy. This was stated explicitly in the given close reason and repeated in the comments. I'm not sure what is unclear about that. The given close reason is:
This question does not fulfill the requirements of a Purim Torah post, such as being distinctly 'Purim' (not serious), distinctly Torah, and distinctly Q&A. For details, see the Purim Torah policy.
Indeed the question does not obey the policy which requires that questions:
- misinterpret a real Torah concept or Jewish text
- apply a distinctly Torah style (e.g. Talmudic analysis) to an irrelevant topic
So clearly the question should be closed. No one has provided any argument against this.
You note that you think that "It would be very troubling if there were fewer than 4 close votes from the community, and a moderator closed it anyway." This would not be troubling at all. Moderators are supposed to close things without waiting for community input if they are supposed to be closed. Why else do they have the power to do so?
The question of why a different question remained open in a previous year is somewhat interesting, but it's important to remember that its being open last year doesn't mean that it would be open this year or should have been open last year. We simply need to check if that question fulfilled the above criteria.
It seems to me, as I described in the comments there, that asking about any irrational number is absurd because there are so many of them. Indeed trivially almost all of them are clearly not significant at all. But I would personally not reopen the irrational number question if someone closed it. It seems like a borderline case to me.
Asking about the Fibonacci numbers as a set (not just any number in that set) isn't funny or absurd at all. It's actually an interesting question IMO. There's no room for debate that I can see about the Fibonacci question. If anyone sees any way the Fibonacci question fulfills the Purim Torah policy please let me know.