I could imagine Palpatine becoming complacent after the Empire was established. Devolving power to governors to crush what little resistance remained. While he himself presumably retired from the public scene to finally devote more time to the dark side of the force.
In his absence governors such as Tarkin rose to great power, standing up to and commanding Vader; and even Admiral Motti saying directly to Vader, "Don't try to frighten us with your sorcerer's ways, Lord Vader. Your sad devotion to that ancient religion has not helped you conjure up the stolen data tapes, or given you clairvoyance enough to find the rebels' hidden fort-..."
The situation is similar to that presented in TFA, as Tarkin expresses: "The Jedi are extinct, their fire has gone out of the universe. You, my friend, are all that's left of their religion."
The Emperor isn't even regarded. If his real powers were known, they now appeared concealed from the masses just as they were during the Clone Wars.