>This would be the equivalent for a pro baseball team laying off their entire roster because nobody on the team showed the growth that those in the feeder teams showed.

This does happen in baseball, not literally the entire team, but Google also isn't laying off everyone. Teams regularly decide to let better performers leave just to replace them with worse players. The reason for this is that the worse players are always cheaper. Many teams are happy to pay a replacement player for half the production at a quarter of the cost. That L9 could have still been productive while not living up to the expectations for someone making that salary.