You need to be quite gullible/naive to believe those big wins. It's a pretty clever way to market crypto gambling sites though.
The way how they spend a lot of money on single bet that tells all that what they do is really unrealistic that's why there's no special feeling when seeing those guys winning a huge amount of money usually they show on their live stream since we know that those win is not real. But unfortunately there are people doesn't know the real schemes made by these streamers since there are newbies which still innocent regarding on the methods use by those streamers so for sure they are the target market of those people and they try to lure them to gamble on the casino they are promoting. So to avoid getting hype we should choose what we want to see and pick those streamers who's shows more realistic gains and showing no sign of they are doing some fraudulent actions towards their followers.