Did Github's "Hardcore Forking Action" contribute to PyGate 2013?

Probably not to any significant degree. Using the word "fork" as a pun on certain other terms has been going on at least as long as these terms have existed in English. The term's use in the software world predates git (and, by extension, github) by years, and the puns were not far behind then either.

It is true that the concept of software forking once had a much more negative connotation than it has taken on since the advent of git. One might say that the open-source software world has generally become more fork-positive, and the pun's use has likewise been altered. Both became more prevalent; that's for sure. But I don't think any particular instance of the term, or even in aggregate, can really be said to have contributed meaningfully to this incident.