[asdfman123]

This whole article isn't very insightful but people upvoted it because they like what the title says.

Google needs to hire generalists because they need to hire any good developer as there's a talent shortage (or at least a talent identification shortage).

And most generalists are generalists because that's what their jobs have required, and can become specialists shortly.

Finally, as a side node, a benefit of being a generalist that the article doesn't mention: you can cross apply good ideas from different domains. You can say "X language does Y -- maybe we could apply that idea to our existing code base. "