National Socialism began with the founding of the German Workers' Party, or DAP, in 1919. The founders were Anton Drexler (who was the de facto leader), Karl Harrer, Gottfried Feder, and Dietrich Eckhart. It began as a very small, almost club-like organization. Hitler attended one of their debates and agreed with many of their positions, chiefly on German nationalism, rejection of the Versailles Treaty, and anti-Semitism.

Hitler spoke in their favor at a debate and impressed the DAP leadership with his charisma, who swiftly made him a propaganda chief. In about 1920-21, Hitler persuaded Drexler to rename it the NSDAP, aka the Nazi Party, and slowly pushed the others out of the way and became the de facto leader himself. After the failed Beer Hall Putsch of 1923, the party was disbanded and only reformed in 1925 solely under Hitler. Drexler, Harrer, and Feder somewhat faded into obscurity (something I found really odd), while Eckhart died before the NSDAP gained momentum.

To TL;DR this, the others didn't have the vision or charisma that Hitler did. He was responsible for getting the party a large following and polishing it into a nationally known organization. It is doubtful that Nazism would have came into being had they not invited Hitler into their group, however. On the other end, Drexler's teachings have Hitler a convenient jump start.