What is the artistic achievement of Citizen Kane?

In terms of film narrative techniques, Citizen Kane broke the linear narrative techniques of previous film sequences, adopted a nonlinear multiple narrative structure, and used narrative techniques such as flashback and interpolation to express the characters from multiple angles and units, making the characters more vivid. Although this brand-new narrative technique is common today, it was unprecedented at that time, thus becoming the dividing line between modern films and traditional films. Wells did not create nonlinear narrative skills. Several Hollywood movies have been tried before, but Wells took this "overlapping bedstead" form to the extreme. Each paragraph has a great time jump and overlap, and many illusions, dialogues and themes echo each other in different paragraphs. Wells even called Rosebud a "liar". Rosebud's motivation is just a gimmick of the plot. The exploration of this gimmick makes the narrative take shape, closely links the chaotic details of the whole story, and provides a dramatic question to catch the audience, which makes the film have the mode of detective film.