I think that before we talk about the gleam and glamour of streamers winning big we should also talk about streamers losing big too. This is the part that is often downplayed. Okay. Now to the topic, what I would say about these streamers is that they play day in day out and at decent stakes. Remember that this is a job to them so they put the hours in as much as I love to play the slots I don’t have time to play like they do so will probably never see a big win in my life time as much as I would love one and I am understand that it is not a problem.
We even had a thread here about one streamer losing a huge amount of money and thinking that the casino he played with was rigged, it's just speculation if we think that streamers are playing on a different platform for them to win, we have to prove that they are, but unless we cannot prove that, streamers win whether it may seem to good to be true are considered valid wins, what they are using may be sponsored money but to think that its rigged to the point that they make the streamers win is not the case.
Up until now there have been no expose or whistle-blowers that stated that casinos are making the streamers wins to gain more referrals if there are videos or testimonials then streamers will lose their reputation and they will be considered cheaters.
Yes the whistle blowers are not yet here to testify the claim, but the problem or argument began when the people whom they refer don't get such wins like the streamers. And from the look of things, if these streamers only won big, isn't it going to be suspicious on the viewers end. Hence, they'll also make it in such a way that they'll lose big too, to make it real and convincing. On the other hand, nobody cares if they lose huge amount, what gets the eyes of people is the huge amount of money they wager and the returns. Since, it's certain and proven that they work for the casinos, then nothing is wrong with the speculative ideas like what OP stated; being favored by the casino allowing them to win often than they lose. You can't for sure know what's happening behind the scene. The whole processes still boils down to marketing strategy. Who knows, they could be professional gamblers, but the results still looks fishy. Other professionals still complain that users don't get the kind of wins the streamers get, what would you call that? Added with the huge amount these casinos hand out to them, they gamble without any fear of losing out. Giving them confidence to take any prediction within their mind, which may turn out to be true. Aside that, being the possibility. I can't succumb to any other idea that's attached to their enormous wins, if not being on the favor of the casino.