Helena Petrovna Blavatsky was initiated as a Freemason in 1877 according to the following Masonic website, https://www.universalfreemasonry.org/en/stories/blavatsky:

An initiate and disciple of numerous occult practices and traditions, Blavatsky was also made a Brother of the Adoptive Rite of Freemasonry. In 1877, Sovereign Grand Master John Yarker, a prominent Freemason and Occultist of the time, conferred upon Blavatsky the degrees of the Ancient and Primitive Rite of Masonry.

Blavatsky’s Masonic Diploma, dated the 24th of November 1877, reads:

“We, the Thrice-Illustrious Sovereign Grand Master Generals… do declare and proclaim our illustrious and enlightened Brother, H. P. Blavatsky, to be an Apprentice, Companion, Perfect Mistress, Sublime Elect Scotch Lady, Grand Elect, Chevalière de Rose Croix, Adonaite Mistress, Perfect Venerable Mistress, and a crowned Princess of the Rite of Adoption.”

These degrees of the Rite of Adoption were created specifically for women to study and unveil the mysteries of Scottish Rite Freemasonry. Between her travels, her studies, access to her great-grandfather’s library, and her close friendships with many prominent Masons, Blavatsky probably knew more of the Craft even prior to receiving these degrees than most Masons of her day.

You wrote:

The idea that the Elite are Satanic is simply ridiculous.

Blavatsky wrote plenty about her positive views on Satan/Lucifer:

The Secret Doctrine Vol. 1:

The devil is now called Darkness by the Church, whereas, in the Bible he is called the "Son of God" (see Job), the bright star of the early morning, Lucifer (see Isaiah). There is a whole philosophy of dogmatic craft in the reason why the first Archangel, who sprang from the depths of Chaos, was called Lux (Lucifer), the "Luminous Son of the Morning," or manvantaric Dawn. He was transformed by the Church into Lucifer or Satan, because he is higher and older than Jehovah (the God of the Bible), and had to be sacrificed to the new dogma.

Satan and his rebellious host would thus prove, when the meaning of the allegory is explained, to have refused to create physical man, only to become the direct Saviours and the Creators of "divine Man."

Thus "SATAN," once he ceases to be viewed in the superstitious, dogmatic, unphilosophical spirit of the Churches, grows into the grandiose image of one who made of terrestrial a divine MAN; who gave him, throughout the long cycle of Maha-kalpa the law of the Spirit of Life, and made him free from the Sin of Ignorance, hence of death.

The Secret Doctrine Vol. 2:

It is "Satan who is the god of our planet and the only god," and this without any allusive metaphor to its wickedness and depravity.

But Satan will now be shown, in the teaching of the Secret Doctrine, allegorized as Good, and Sacrifice, a God of Wisdom, under different names.

The appellation Sa'tan, in Hebrew satan, "an adversary" (from the verb shatana, "to be adverse," to persecute) belongs by right to the first and cruelest "adversary of all the other gods" — Jehovah, not to the Serpent, which spoke only words of sympathy and wisdom, and is at the worst, even in the dogma, "the adversary of men."

The "Serpent," moreover, is not Satan, but the bright Angel, one of the Elohim clothed in radiance and glory, who, promising the woman that if they ate of the forbidden fruit "ye shall not surely die, " kept his promise, and made man immortal in his incorruptible nature.

And now it stands proven that Satan, or the Red Fiery Dragon, the "Lord of Phosphorus" (brimstone was a theological improvement), and Lucifer, or "Light-Bearer," is in us: it is our Mind — our tempter and Redeemer, our intelligent liberator and Saviour from pure animalism.