I'm not sure that's true. Microsoft and Amazon, for instance, did pretty well in Seattle. And Pittsburg does have CMU, whose CS program comes in right after MIT, Stanford and Berkeley's. It was probably easier for Google in the Valley. How much easier is hard to say.
It was only easy for Google because the had tons of cash to hire people when everyone was getting laid off in the tech bust. They owned the market for top people because of the rare event that many top people were on the market.
