If the executive team doesn't let staff go they will be fired by the board. If the board doesn't fire the executive team they will be voted out by the shareholders. If the shareholders don't vote out the board the stock price will plummet and in the best case scenario what's left of Uber gets vacuumed up by another company or activist investors and they go back to step 1 minus any of the severance packages and good-will.

It's horribly sad to see mass layoffs but the alternative creates a lot more chaos.