Dear Yankel,
“For thousands of years – since matan torah – we had one thing and one thing only- in our public domain. Nigleh . Even though Nistar is an integral part of the torah , it was not in the public domain . this started to change from the time of the publication of the Zohar , the earlier Mekubalim, the Ari and his disciples , but was mainly popularized since the advent of the Baal Shem and his talmidim.”
Farcical, erroneous, pure fiction.
For the first thousand years after Mattan Torah, there was so much Esoteric Torah that the revelation of the Zohar would be nothing but an opaque curtain to hide the Toras Haniglah. The next thousand years was the formation of our classical books. There is only one work that sticks to niglah = The Mishna. There is a parallel work that only sticks to nistar = Sefer Yetzirah. If we had to divide all the works of this period into nistar versus niglah, two thirds of it would be nistar. But that is only what survived. Using historical analysis, we know that while some niglah was lost only some nistar survived.
At that time, there wasn’t anything in the public domain. An individual had to come to Bais Medrash to learn Torah. A rebbe could refuse to teach a talmid that was not up to the material, but there was no ‘hiding’ of esoteric teachings. See the public sermons that have been preserved in the Midrashim.
The major change is the rise in universal literacy. Even when The Zohar was printed, it was not legible to most of the lay people because of unfamiliar terminology and obscure abbreviations. The Baal Shem did not advocate spreading Kabbala any more than most of his contemporaries. His contribution to Lurianic Mysticism was his insistence not to spread the other versions of Kabbalah. The Polish Mekubalim of that era had a potpourri of teachings that were contradictory and of unknown origins that were being widely disseminated. The nearby countries had many kabbala tinged public speakers and books. Germany was going through a downturn in Torah study in general, but the Shelah was already a prominent sefer.
I don’t see why Chabad is the issue when you have complete goyim studying The Zohar and Arizal and publishing in all languages.