From the perspective of someone who wants to create a narrative, and doesn't care overmuch about the truth, allowing comments on articles is just a nuissance. If they express a point of view contrary to the narrative, you have to waste time moderating them down so they can't be seen, or (in extreme cases) actually replying to them. So you just post a fake comment or two, scream "think of the children!!!" and shut it down. Or you just wait for that one mentally ill guy to post something crazy and just point to that. Same result.
It's the same tactic news sources use in other contexts, too. You want to create a narrative against candidate or political party X. So find a really loathsome person who supports X and run a story about them. Perfect. Never mind that most people affiliated with X woud never associate with that person.
