First of all, you didn't really do anything wrong, it's simply how it worked out in the system. But let's analyze this step by step.
What you did was raise a close-flag. A close flag does not call any moderators to action (neither does anyone explicitly mark it as "helpful/declined"). All it does is enqueue the question into the close voting review queue, to be reviewed by other users with the close-voting privilege (3,000 rep). And at this point in time you were right to issue the flag, since the question seemed pretty unclear (and other users did so, too).
So what happens with the close-flag. Once any user with closing ability votes to close this question (after you issued your flag), it will automatically be marked "helpful" (even if the question doesn't actually get closed, I think). On the other hand, once three users (or one moderator) vote "Leave Open" from the review queue and noone voted to close, the flag gets automatically marked as "declined" (and the question is removed from the queue).
Now what happened here specifically was that some users issued close flags for the question but noone voted to close yet. Then someone repaired the question into a sufficiently valid state. And after that I encountered the question in the close-voting review queue and voted "Leave Open", since it wasn't unclear anymore. So while you might have been right to flag it as "unclear what you're asking" at the time this question was unclear, that flag simply was a victim of the circumstances and the specific order of treating the question. If anyone had actually voted to close the question before I removed it from the queue to stay open, your flag had been "helpful".
