It's hard to break any writer's mold without sounding like an arrogant literature professor, but I'll give it a try.
First of all, it's worth noting that King's conversational style (that "storyteller" vibe everyone is talking about) is carefully crafted. Peter Straub once said that Stephen King was the smartest man he had ever met. He went on to say that the narrative voice in King's novels is Stephen King's greatest creation.
I emphasize this point because Straub is very careful in his choice of words, noting that King's narrative style is both purposeful and carefully crafted.
Secondly, I think we should consider the views on writing expressed by King in his book "On Writing". King makes it clear that for him, the story is his own. Story is more important than character development, dialogue, setting, theme, etc.
This had a profound impact on his style, as other elements were replaced by story. For King, any description or action that doesn't advance the story will be removed.
(Note: This should not be taken to mean that King wrote, as James Patterson said, all B-grade action movies. There is a lot of that in The King. But It's important to realize that King chose descriptions based on the story, and if it didn't add to the story, cut it out )
Third, the influence of poetry on King's prose is generally overlooked. I think this was a mistake. King talked a lot about poetry and its impact on him over the years (he was attracted to his wife because she wrote poetry). He also frequently quoted poets such as George Severis and William Carlos Williams.
King did learn to emphasize image from poets such as Williams. When King describes a scene, people often say it's like he has a "movie projector in his head." A more apt metaphor is that King recorded details like a modern American poet: concentrating on a single image that represented the whole.
Finally, we should look at who influenced King's style. King identified the three most important writers to him as Richard Matheson, John D. Macdonald, and Don Robertson. He also mentioned several times the influence of Theodore Dreiser and Frank Norris.
If you read MacDonald and Robertson's book, you will clearly see the conversational style that King honed over the years. In the work of Dreiser and Norris, you can see King learning to value fiction over the "literary styles" so often praised by critics. Dreiser's prose was not beautiful, but the man could tell stories like no one else.