Although Adolf Hitler was raise Roman Catholic (and for some time in his childhood sincerely thought of entering Catholic monastery and someday becoming an abbot), he was a theist.
More specifically, a monotheist, because he believed in one Almighty God – the Providence. Whom he did not associate at all with the Christian Trinity. Possibly because the latter (and the whole Christianity) was fundamentally incompatible with Pan-German nationalism and Aryanism – his personal ideology.
One form of mysticism is a direct personal communication with a specific deity (e.g. with the Absolute, the Infinite, the Cosmos, the Universe or God) or spiritual entities (e.g. saints).
Adolf Hitler communicated with the Providence on a regular basis which made him a genuine (and powerful) mystic. There is no evidence that Adolf Hitler ever prayed (publicly or privately) to this deity; he only listened to it for an advice, guidance or outright command. Which means that Hitler spent a considerable amount of time in a meditative state of mind (meditation is a fundamentally mystical practice).
When you deal with the Almighty Providence (and Hitler did believe that his Providence was, indeed, omnipotent), you do not need – or want – to deal with any other spiritual entities or forces.
Consequently, it is no surprise that he rejected any and all forms and practices of occultism and paganism (polytheism) and after he came to power in 1933, ruthlessly suppressed both.
True, there is indisputable evidence that Adolf Hitler was once an avid reader of Ostara – the occult and anti-Semitic magazine published by an (in)famous political and racial theorist and occultist (and a pioneer of Ariosophy – esoteric ideology) Adolf Josef Lanz (and even visited the office of Ostara asking for back copies).
However, Hitler was interested strictly in ideological aspects of Lanz’s teachings and could not care less about their occult roots and foundation.
It is also true that the German Workers’ Party (DAP) that Hitler joined in September of 1919 was a creation of an occult Thule Society. However, there is no evidence that Hitler was a member of this society or even ever attended its meetings (actually, there is a strong evidence that he was not and did not). Or even met with the prominent members of the Thule Society (other than with the DAP founders).
In fact, right after he became the Führer of NSDAP, he immediately severed all ties with the Thule Society which subsequently went into decline and was officially dissolved in 1925 – long before Hitler came to power. By that time he could afro the breakup as he found far more powerful sponsors – wealthy and influential Germans and – first and foremost – the Reichswehr.