"Corporate greed" is a thought-terminating cliché. Why did "corporate greed" start happening all of the sudden? Why did those companies overhire, and why aren't they doing that any more - did the corporate greed go away? I suspect that what OP nebulously refers to as "corporate greed" is actually multifactorial - a behavior determined by a complex interaction of incentives and factors. Someone else mentioned tax law changes, which is an obvious one. Can we think of more?