[Kliment]

I think it's a side effect of many people submitting the story rather than explicitly upvoting it (in which case upvotes would cluster around one or two stories, as they do for the top ones). Since submissions count as upvotes, and there's a critical mass of people submitting each version of the story, they all end up on the front page. You'll notice there are a couple where the comments are alive, but in a situation like this (single story, many sources, many people submitting each without checking if it's already there), this is exactly what would happen.

It's also possible some people are hoping for a karma boost by submitting a story many others are likely to submit, and thus there is an incentive to submit a story on the gamble that noone else has done it yet, since many others are likely to submit it too.