Leon is very impressed with Hubbard's 'Four Conditons of Existence', yet that's a rewording of the Kabbalistic Tetragrammaton. (See 'Sole Source Myth' thread).
Hubbard's 'The Factors' is a re-write of Crowley's 'Naples Arrangement', complete with Hubbard's addition of "Affinity, Reality, Communication" in the same place as Crowley had inserted the yogic "Bliss, Knowledge, Being."
And Crowley's 'Naples Arrangement' was, itself, a re-write of older Kabbalistic (and other) ideas, with Crowley's addition of a bit of Yogic teaching.
Hubbard removed the earlier part of Crowley's Naples Arrangement which posits a primordial 0+ and 0- (boy and girl "zero") which somehow generate a kind of pre-cosmic tension that begins the creation of (a) (the) universe.
However, Hubbard kept Crowley's insertion of "Bliss, Knowledge, Being" which became "Affinity, Reality, Communication."
Bliss, Knowledge, Being is inserted in the same place that Hubbard later added "Affinity (Bliss), Reality (Knowledge), Communication (Being)" to his 'The Factors'.
From Crowley's 'Book of Thoth':
"These ideas of Being, Thought and Bliss [or Bliss, Knowledge, being] constitute the minimum possible qualities which a point must possess if it is to have a real sensible experience of itself..." :
http://www.etarot.info/naples-arrangement
One interesting detail in the development of Scientology is Hubbard's contact with OTO member, student of Aleister Crowley and the Occult, chemist and (literally) rocket scientist, Jack Parsons, and the extent to which Hubbard "picked Parsons' brains" is impossible to determine. As a side note, I'll add that Parsons wrote to his former girlfriend, Sara, after she had divorced Hubbard, and according to a reliable source that I cannot reveal [sorry, but I cannot], Parsons wrote that Hubbard had visited him, and stayed with him for a time, after Hubbard's return from Havana, Cuba in 1951. It was immediately after that period that Scientology burst upon the scene, with a re-writing and a re-working of ideas earlier expressed by Crowley.
Hubbard also borrowed from Korzybski's writings, and 2nd ("erased") wife Sara (1946 -1951) would sometimes read to him from Korzybski's writings.
The notion of an "ARC break" and remedies for "ARC breaks" is a spin-off of Korzybski's notions on resolving upsets.
However, Hubbard also used "ARC" manipulatively.
And ARC, in Scientology, is subordinate to "KRC," with ARC being the lower triangle of the "S with the double triangle" Scientology symbol, which is a re-expression of Crowley's "Love is the law, love under will."
And there are many more correspondences with earlier subjects.
I've no issue with Hubbard having had flashes of brilliance and innovation - including innovation of a positive nature. My problem is with what he did with the "total package" that he molded into Scientology, and with his hidden agenda. A hidden agenda that corrupts the entire subject, and that corruption crawls inside the heads of Scientologists and corrupts them also.
From L. Ron Hubbard's 'Data Series 1', 26 April 1970:
"As Alfred Korzybski studied under psychiatry and amongst the insane (his mentor was William Alanson White at Saint Elizabeth Insane Asylum in Wash. D.C.) one can regard him mainly as the father of confusion."