That's the take in this NY Times analysis: low interest rates encouraged over-hiring, and this year's rising interest rates encouraged companies to pull in their horns.

But I think there are other mechanisms at work too. Google, for example, is in no immediate cash crisis: it could have shut down some projects and shifted personnel to other projects (as it does regularly), it could have continued with its hiring-near-freeze, it could even have taken advantage of layoffs at other tech companies to hire some good people at a discount. But then investors might have fled from Google to the other tech companies that did announce layoffs.