In SEDE for Stack Overflow, I see that out of the 342 moderator nomination posts in the PostsWithDeleted table, none of them have a deletion date. So either disqualified candidates don't show up the way I would have guessed, or no candidate has ever been disqualified on Stack Overflow.
@JourneymanGeek there was one who got disqualified in the very recent past, causing huge drama all over the place. So, 1) @Tanner there was at least one on SO, and 2) I'm pretty sure the nomination posts are handled in different way when deleted, maybe even redacted, so even high rep users won't be able to see them anymore. 3) Don't think we can know how many have been disqualified, and doubt staff will share such detail.