This question was put on hold as off-topic.
Yesterday I flagged it as off-topic before it was put on hold:
Yet it was declined.
Why is this?
Not everyone sees on and off topic the same.
That's why we have votes and even a close or delete isn't permanent. I did cast a binding reopen vote to give that question a second chance and it's closed pretty quickly as off topic and I respect those votes as it's not a great example of an on-topic question.
Flagging is for very serious issues that require a moderator to take action and circumvent the normal process. As you can see from the history on that post - the normal voting process to close / reopen is sufficient here (and working quite well IMO) to handle this post so declining to take action just lets you know to use the votes and comments and not flag something that can be handled with normal votes. The moderators don't need to intervene in this case, hence the flag was declined.