its astroturfing by for profit companies. after the election, they realized: a) that folks were filtering out the astroturfed subreddits in /r/all, and b) that r/all's filter list has a hard limit of 100 subreddits. so, they switched tactics - by astroturfing >100 subreddits, they can guarantee to their clients that their posts will make the front of r/all for everyone.