Nonpolitical: Obviously, he relied on chassidus. It’s not like his Rebbe the GR”A was familiar with the Zohar and Kitvai HaAri, he needed the Baal HaTanya to explain it to him. Nebech.
Spoken like someone who has never gone through the NH nor the Tanya. The NH is not Kaballah rather it is based on Kabbalah, the same as the Tanya (and Chassidus in general). And as is the case with anything that is based on something, there is a hermeneutic that predisposed any interpretation; this is what I meant by saying the NH is based on the Chassidus. If you would like to see exactly the extant that he based it, there is a new NH that just came out which endeavors to show the general sources (not strictly Chassidic ones) of the NH. If you would go through it you will many novel interpetaions of the NH are actually taken from early Chassidic texts. So unless the NH was mechaven to chassidis by himself he obviously took it from there. (At the minimum there are many places where he deviates from the Gra himself, e.g. 3:7).
{In the future before making away with what someone says, make sure you check your facts)