Perhaps Google as an employer shouldn't allow employees to choose any name they like, and do some diligence to avoid name clashes. This may sound quite reasonable for outsiders, but internally this will be another step that requires manual review in the process of publishing open source code, and employees will see this as red tape and get discouraged from open sourcing their code in the first place.
The benefit of requiring every project to go through a name clash review is also questionable: there are 2.5k repos under https://github.com/google, and most of the them will never become popular enough for name clashes to be a problem anyway. This repo only has 177 stars despite hitting HN homepage.
IMO Google should instead make it easy for people to publish their open source code wherever they like, but I suppose there are some messy legal reasons why they prefer employees to put their repos under https://github.com/google. (It's not a hard requirement, but they do make you jump through extra hoops to open source your code elsewhere.)
(I'm a Google employee, but I didn't know this project and don't work for the department responsible for the process of open sourcing code.)
Now perl stealing prolog's file extension on the other hand...
There is nothing nefarious here. There is no cabal. These things happen all the time. I've had it happen to two of my own small/obscure projects. It happens.