Frumteendex: Chasidish, Livish, UO, and me?
The Kabbalists -- way before the Chasidim -- also taught that Hashem Himself sometimes helps this process by revealing to the leaders of certain generations, certain teachings that were not previously available even to perhaps greater leaders in greater generations, because those teachings are revealed only when they are needed by the specific generation.
This, they have said, is why the Zohar and Kabbalah was made available when it was, and not before. The Rambam (at least for most of his life) and Rav Saadiah Gaon did not have the Kabbalah, because they did not need it for their Avodah.
The Ramchal writes this in response to the claims that were leveled against him that he must be a faker because the supernatural revelations that he had were not had even by the Arizal himself. The Ramchal answers (in his letters, Ramchal Ubnei Doro) that although he does not compare in the slightest to the Arizal, since his (the Ramchal's) generation was in need of those revelations, someone is chosen, in this case the Ramchal, to be the recipient of those revelations, to be used for the needs of the generation.
And so, when you see such an idea in Chasidishe Seforim regarding Chasidus, it is neither new no Chasidic in origin.