"Conspiracy"? Yeah.
"Theory"? Well, it isn't a "theory" any more. The evidence that it was (and is) being done is extensive and compelling.
One of the things I see these days is that there are a bunch of people who will just mindlessly repeat some catch phrases, whether or not they even understand them. "Fake news" didn't start with Donald Trump saying that about CNN. It really happened. It wasn't just unfavorable spin from a network that was unfriendly. It was just plain made up stuff, being passed around the internet, masquerading as news.
Now, however, people use the phrase mindlessly to label politically unfriendly media outlets.
We saw it earlier with "crisis actors". That phrase has a meaning, and idiots on the internet actually claimed that the Parkland kids were crisis actors. That's ridiculous. However, the claim has been repeated by people who don't even know what a crisis actor is. The right wing doesn't hold a monopoly on this, either. It's kind of disconcerting, that people repeat lies so easily, without even understanding what they are saying.
But, to Captain Howdy. Yes. Trolls and bots really have been injecting fake news stories, not just unfavorably spun stories, into the internet, including about the Parkland kids. I don't know if you have fallen for any of them, but it is really happening, and yes, Russians really have been behind a lot of it. (I don't know if specifically the fake stories about Parkland have evidence of Russian involvement.)