Here is a very literal answer to the question: most flags that aren't explicitly for moderator attention are dealt with in the review queues by users of the site who have access to those queues. That means other users are the jury here, which puts you at their mercy. In this case, three users said that it looked okay, while two voted for deletion. Three "looks okay" votes are enough to finish the review in this case.
Getting in to why three users voted that it looked okay is a whole other thing. We won't know unless they share their reasoning, and there are lots of different potential explanations (disagreed, thought it was bad but did not merit deletion, didn't see the issue, cat ran over keyboard, etc).