If you check the revision history or the timeline of your post, you can see that the question was bumped by the Community user.
You can find pointers to some information about community user in the corresponding tag-info.
In particular, you can check the user page of this user. And also the FAQ post: Who is the Community user? There are also some related discussions on this meta: Modified by Community and Auto-bumping of unanswered questions.
Community user bumps posts which have answers but none of the answers has positive score. Quoting from the answer "Community ♦ seems to be bumping new questions more frequently than usual":
Note that the posts eligible for bumping are those scoring >= 0 that have gone at least 30 days with no activity, have at least one non-deleted answer scoring 0 and none scoring more than that, and no accepted answer (also, they can't be deleted or closed).
I am not sure whether Jeff Attwoods answer "Community ♦ should discriminate more when bumping unanswered questions" is up to date, but it at least sheds some light onto the criteria how the community user chooses which question to bump:
Right now it takes the top 100 unanswered questions with no recent activity by views, then picks randomly from within that group.
Here is a SEDE query listing questions bumped in this way: Questions recently bumped by the community user. (I will remind that the data in SEDE are only updated once a week, so it shows the status from the last update.) If we check how many times was some question bumped by community user, this specific question is in top 50.