Neither do I. I guess some guy became a moderator and wanted to try his new powers at random, or something.
That's not how it works. Anyone can flag a post (with proper reasoning - misuse gets you banned), at which point it gets put in the moderation queue again. The fact that it got deleted means that noone wanted to approve it, either because they agree with the flagging reason or because they didn't think the quality was good enough (which happens to be the flagging reason as well on this post). A quick check on recent posts with status:deleted show that posts in the moderation queue get reviewed by around 5-10 users with approval priviliges (this tally gets removed automatically after a certain time, which is why you don't see it here).