I would love to see some internet detective to do a list of how many of these vievers are paid viewers or bots. I've been a part of a team that did that, i mean commented on streams, followed and engaged for money, just to get algorithms picked up these streamers on top of list.
And after that, algorithms take care that traffic brings more traffic, because algorithms thin it's worth watching. Crowds will bring more crowds, That brings referral money, and money brings more money, as some casinos start to promote them to view their casino in the stream. It's a weird world out there and weird opportunities to make money.
It may seem odd but this is a process that even happens in the real world all the time, the bigger something is the more of it brings regardless of what that may be, so in the case of viewers if there is a slight increase of viewers for a particular video then algorithms will pick this up and show that video to people with similar preferences, which will watch the video, increase its popularity and then the video will be shown to even more people.
That is basically the reason why a lot of YouTubers tend to either buy views and interactions or try getting a lot of fake views and interactions from free websites providing such services, it sometimes works for them but most of the time the hype dies very soon and their channel gets a hard decline which they barely be able to recover from. That is the reason why it is important for someone to first learn doing SEO and optimizing their videos well.
A lot of successful YouTubers never used a wrong way of accumulating viewership and they are pretty successful today because they've worked really hard. There is basically no shortcut to success and if you want success, you will have to spend a lot of time and show a lot of dedication to achieve it.