Why are there so many disgruntled postal workers?

What you stated is exactly what is causing problems...workers hating their managers, there is too much work, more hours added to existing routes, being fired for no good reason, undue stress, inadequate background checks...I know for a fact, in my local post office every day the lines are out the door, there are less people working the windows resulting in much longer waits, If anything you would think there would be customer rage instead.