Deleted posts are at first just hidden from public view. To steal the ID from such a post, the deleted post is given a new ID. The deleted spam post in this case now has ID 57394364.
After about a year, deleted posts are moved off of the live database and into an archive database, and no longer occupy their original message ID in the live database. After about another year, deleted posts are deleted from the archive database as well, though they will probably still exist in offline backups.