Nothing is ever truly original. The core idea that the Buddha brought to the spiritual sphere of the society of the Indian subcontinent is that meditation is a faster path to enlightenment than other methods.
People knew about meditation. People knew about enlightenment. There were already a thousand years of sustained theological inquiry into the subject before the Buddha made his determination.
So what happened? Well usually in these sorts of situations a number of things come together. Society has to be ripe for the new movement. Indian civic life has finally reached the point where it could afford to have large groups of people to have leisure time, and therefore the ability to self-improve. Writing technology has evolved to the point where theological discourse could be much more easily and economically shared.
Finally, the Buddha himself, an amazingly charismatic, humble figure, what we in the West might call, “Christ-like.” This is the sort of confluence of events that made that part of history so fascinating and influential. Humanity has just learned how to walk, now we’re forming sentences and learning what right and wrong are.