This seems to be a common thing with aggregators in general. As someone who's seen their work posted to Reddit and other sites (or has posted it there themselves), the aggregator topics seem to get a lot more views and comments than the source article does.

I think in many cases, the system comes down to "upvote the topic and comment if I agree with the premise (or what seems to be it), or downvote the article and comment if I disagree with the premise (or what I think it seems to be)"

This is because you are reading comments of people that write comments. People that write comments, (usually) read comments. There are lots of people that read comments that don't write comments and probably even more that don't read comments and click on the links.

For the last group, the votes and number of comments are just signals for how good the link is - they don't care about the comments.

It is not that simple. For one, I only put the first comment under an article after reading it. Which does not happen until I am interested in the topic.

I mostly rely on top level commenters replying to the article content, often with quotes, and then go down into discussion from there.