I am the Product Manager for GitHub Pages. As has been mentioned multiple times here, the usage limits were not in response to a specific external event. The limits have been an internal policy (in one form or another) for as long as I've been involved (nearly 4 years now), and we chose to publicize them in a series of updates beginning early this summer.

This is a classic case of "this is why we can't have nice things". If you're using GitHub Pages for your personal site or to document/talk about the work you're doing on GitHub, in general, you should be fine, even if you get HN-level traffic every once in a while.

The problem comes when a small handful of users use GitHub Pages for things like automated version checks or configuration distribution, as a makeshift ad CDN for for-profit sites, pushing an automated build every minute, or to distribute large assets (for which things like Releases are a better fit).

When a user (ab)uses GitHub Pages in a way that threatens our ability to build or serve other users' sites, technically or practically, we need to step in, and those posted limits are intended to help set expectations as to what you should and shouldn't use GitHub Pages for. But again, the vast majority of the nearly 1M users that use GitHub Pages will never hear from us (and in most cases when they did, we proactively reached out and provided ample warning/offered to help).