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.
