The 1950s saw the end of the old movie studio system where the moguls like Jack Warner and Louis B Mayer had shepherded an enormous number of stars through the film process to the American public. I use the word 'shepherded' for a specific reason. The stars under contract in the old studio system were treated like slaves, albeit very well-paid slaves during the '20s, '30s and '40s. The Great Depression occurred in the 1930s, and many people would have given their right arm in order to receive the sums that these American movie stars were making (often thousands of dollars a week, a sum that represented a fortune in those days, and isn't anything to sneeze at in 2013, either!).
Bette Davis went to London, England to fight to get out of her contract because she was unhappy with the roles she was being offered. She did not win technically, but upon her return, she did receive better roles in better films. A couple of years after her fight with Jack Warner, her boss and head of Warner Studios, she starred in such films as Jezebel, Petrified Forest, Dark Victory, Juarez, The Lives of Elizabeth and Essex, The Sisters, etc. Then after that she really kicked into high gear with The Letter, All This and Heaven, Too, Now, Voyager, etc.
In the 1950s, this studio system had largely disappeared because the regulation authorities were concerned that there was too much of a monopoly in the film industry. But it was a tragedy for the film industry that this happened, in spite of what many actors thought. The Jewish moguls who practically invented the film industry treated the movies like they were a factory with assembly line and everything. This may not have satisfied all of the artists involved all the time, but it made for a fantastic product with the moguls figuring out what the American public wanted, and then giving it to them.
They figured out how to typecast the actors, and then just changed the story a bit to accommodate a new picture. So Bette Davis was the neurotic witch (not really 'witch,' but I didn't want to swear!), Garbo was caught between a young lover and old man, and if she chose the young lover, died, Katharine Hepburn basically played herself (to wonderful effect!), and Joan Crawford's persona changed over time from shopgirl to the more mature roles of the '40s.
It was a wonderful time for the movies. Actors often don't know what is good for them. After 1950s, the number of entertaining movies drops considerably, and after the 1960s, it absolutely plummets. In order to compete with television, in the '50s, the films started being shown with that awful black space above and beneath the picture. The glamour was gone.