I'm not sure what you mean when you say Emerson's style and philosophy was so clearly different from others. Emerson seems to be the quintessential transcendentalist. He embraced all of the romantic ideals of his time. He believed in non-conformity, self-reliance, valued intuition over reason and loved the beauty of nature. He did not write poems, novels and short stories as some of his contemporaries did, but his essays promote the same ideas as Thoreau, and even Hawthorne and Longfellow. The differences Emerson might have had with his fellow transcendentalists fit perfectly with the romantic philosophy of independence of thought. Emerson is lumped with other transcendentalists because he agreed with so many of their ideals and many others were influenced by his beliefs.