<sup>Possibly this is closer to a comment than to an answer - however, it would probably be too long for a comment.</sup>

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?](https://meta.stackexchange.com/q/5221)

> You can't delete your own *question* if it:
>
- has an [answer with upvotes](https://meta.stackexchange.com/questions/74466/does-systematic-self-deleting-need-to-be-prevented/74471#74471) (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](https://meta.stackexchange.com/questions/306966/changes-to-bounty-rules-removal-of-double-rep-retention-blocking-of-owner-dele)