Your flag caused the question to be put in the review queue. Three high rep users then reviwed the question and decided it should stay open. The community user bot then declined the flag.
Had you flagged it for moderator attention, I would have declined the flag for "flags should only be used for things that need moderator attention". Moderator flags basically are a way of asking a moderator to act unilaterally. They are great for clear cut cases. In a case like this, as a mod even if I agree and think the question is a bad fit, with 15 upvotes, 1 down vote, and an answer with 55 up votes, I am not going to act unilaterally.
It is worth noting that after you left your comment, someone voted to close, and it went through the review queue again. Three users (at least one new one) reviewed it without recommending to close the question. It seems the community likes the question.