Re: I wonder, how that is possible because if I remember right, questions that have an answer can't be deleted.
If a question has more than one answer or at least one answer has an upvote, it cannot be self-deleted.
From the FAQ post How does deleting work? What can cause a post to be deleted, and what does that actually mean? What are the criteria for deletion?
You can't delete your own question if it:
- has an answer with upvotes (even if that answer has a net zero or negative score)
- has an accepted answer
- has multiple answers (even if there are no upvotes)
- has an answer with an awarded bounty