Google has been decentralized for a long time. Seattle, NYC, Zurich, and London are all big offices that are at least comparable to Mountain View, not to mention a bunch of other smaller but very serious offices.
Facebook, Google, and Apple all have large or rapidly growing presences in Seattle. It does the real estate market and traffic no good, but it is what it is.
You can’t just include Seattle (Fremont), you also have to consider Kirkland, which is much bigger than Fremont. They are building (or have built?) a new larger office in South Lake Union (5 buildings), I’m not sure if they will be consolidating Fremont but I’m pretty sure they aren’t going to consolidate Kirkland.
Altogether Google employs 4500 in the Seattle area, and that number will increase substantially when south lake union comes online. And of course, Google will just be a small presence compared to the other craziness in South Lake Union (Amazon being the biggest, but also Apple and Facebook having large presences).
Now, 4500 in Seattle, 4000 in Zurich, 3,500 in London, 7,000 in NYC...that easily approaches the 23,000 in Mountain View.
The Kirkland and Fremont offices are only 12.4 miles apart. When they move to South Lake Union, they'll only be 9.8 miles apart (and a much better freeway connection).
Facebook, Google, and Apple all have large or rapidly growing presences in Seattle. It does the real estate market and traffic no good, but it is what it is.