The HN internals are kept a bit opaque. Some users can flag, and then IIRC it can be "vouch"-ed for once, where it might be re-flagged again. Upvotes may factor in. Mods will occasionally override manually. Luck of the draw is always a factor.

I'd say that the bias around the Weinstein stories were that they were simply very hot in the mainstream, and that caused otherwise off-topic posts to catch some traction here.