At least some part of it has to be the amount of attention these news pieces get on wsb itself. The subreddit has about 1.5 million subscribers. Any news piece by Bloomberg or Wallstreetjournal talking about r/wallstreetbests instantly gets posted over there and usually garners huge amounts of upvotes. Pretty much free traffic/ad impressions.
Example: https://reddit.com/r/wallstreetbets/comments/dj5xru/u_did_it...