Is DEMOTION a normal thing in a workplace if it is under new management and going in a new direction..........?

..........even if the demoted has done nothing but all his/her best for years before the changes? Do know anyone who had experience this? I know that my father has (he worked in a plant, he had an office, now it's been transformed into a storage room, and therefore he now just a plant worker w/limited office work). If you have that experience, please explain yours.