People over at SRD (SubredditDrama) have shown some fairly convincing evidence that /r/the_donald has some pretty serious vote manipulation going on, which probably has to do with it. And really, honestly it seems fairly obvious once you go on /r/the_donald and realize that everything has around +1800 to +3500 upvotes, but with significantly less comments then it should have (Usually in the 100's or less).

All that said, I though that there was a limit on the number of posts in /r/all that could be from any one subreddit - so I think it's likely that the above along with another factor is the cause.

More realistically, some developer fucked up some logic in the new algorithm which is supposed to ignore most of /r/The_Donald for the election.