There is a small chance that a case drops for you which is worth $5-$40 depending on which map you are watching that contains "Souvenir" items for the event signed by the players.

You only get drops if your Steam account that owns the game is linked to a twitch account that is watching, and is IP restricted (you won't get more drops unless you watch from different IPs at the same time). View botting exists, but it requires a lot of time/money to do, and the Twitch viewership numbers are actually more accurate than you would think.

I'm pulling numbers out of my ass but I would really be surprised if more than 100,000 of those viewers are duplicate accounts. To do the duplicate viewer thing you need to own multiple accounts with a copy of the game on each one.