Back when I was in university, early 2000s, I used to make posts for this company between classes. Here's how it worked, let's say you had a forum like the Farms and you want it to appear as if there's a lot of activity to attract new users. You'd buy a block of posts from this company who would send users like me to your site to fill your order. In turn, the company would pay me five cents a post, sending a paypal payment when you reached $20. You'd just link your username on a target forum, start a bunch of slapfights and make like $2 killing time on the computer between classes. I was doing it more for something to do than for the money as it only paid around a dollar an hour. After a month or so you could buy some random shit on ebay out of what they paid you.
Now that was before the Internet was highly commercialized and politicized and people where just looking for users for their little personal forums.
I'm pretty sure today they pay people to go to Reddit, 4Chan, Youtube or other social media sites and make posts promoting particular political ideas. So many of the people you'd get in slapfights with on Reddit or Youtube are probably just getting paid five or ten cents to post a counterpoint to your political argument in order to push certain ideas on behalf of a political think tank.
I'm also pretty sure a lot of articles on sites like Huffington Post, Ars Technica, videos on Youtube etc are paid for by either corporations who want to promote their products, think tanks who want to promote their political ideas or PR firms who want to promote specific people.
The mainstream internet has just become a series of people getting paid like a dollar an hour to gaslight you into buying into ideas, people and products.
Maybe bots have gotten more sophisticated and instead of paying Indians and students a dollar an hour, you just give these companies money and the set up a fleet of shill bots to push your shit, I don't know. I know I've run into my fair share of posters on site like Reddit who will repeat a talking point over and over in political discussions. They'll word it a little differently each time they reply to someone, but never reply to anyone who offers a counterpoint.