They aren't cutting staff because they made a ton of money. They are cutting staff because they see trouble on the horizon and are positioning themselves for that. Layoffs are rarely lagging indicators. They are more often predictors of trouble coming. This bubble will explode, MSFT wants to survive it. Thats all there is to it.
This may be so but what others in this thread are trying to point out is that this is a relative novelty. Decades ago, layoffs were something that hapened at struggling companies trying to stave off bankruptcy (or already in it). It is a major cultural change to treat employees so casually as fat to be trimmed.