Mass layoff decisions like this are typically made at a higher level of the organization. The executives don't give much advance notice to the middle managers who make hiring decisions for most engineers in order to prevent leaks.
It seems like a bonkers practice to me. I understand that it is important to hire good people. But this could be delegated several levels down, at least for entry-level hires. I suppose the top dogs could worry about promotions and hirings starting at the level of the junior managers, if they wanted to.