My initial idea was that they are manipulating the rating, intentionally insta-dying when off-stream to get to low ratings where they are facing literal newbies they can slaughter. But this guy who published his study on reddit had a much better idea. He watched streams and wrote down the names of the players killed by the streamers. He have found that the same names come up again and again. This has one explanation: the streamers run bots or hire players to get into their games and then die to them. The bot commander or the various hired players watch the stream and rush to the location of the streamer, giving him kills and loot. I wouldn’t be surprised if they’d also act as bodyguards or baits to protect the streamer from players around.
Of course this trick also need rating manipulation, the farmed account must win when not on stream and the streamer must tank his rating to at least average so they can play together.
Anyway, it’s another reason to not watch streams for learning to play. These streamers aren’t good, as evidenced by their low position on the rankings. They are clowns who set up funny scenes with paid actors for the laughs. If laughing at hilarious kills of other players, is your thing, go watch them. But trying to learn to play from watching them is like trying to learn the history of the feudal age from watching Game of Thrones (hint: XIII century France did not have dragons).