Question: According to Kabbalah, what has been the "glue" to Jewish survival?
Answer: According to Kabbalist Rav Ashlag, the purpose of Judaism and the people of Israel is to serve as a sentinel in using the wisdom of the Torah and Kabbalah and to create a better world. The real purpose of Judaism then is to teach this wisdom forward to all people. From a Kabbalistic perspective, it is precisely this purpose or "glue" that has held Judaism together and kept the Israelites going. As long as the Israelites stay true to their purpose, this wisdom continues to survive.
For further reading, I recommend Rav Yehuda Halevi Ashlag's "Gift of the Bible" and "An Entrance to the Zohar" in which this concept is explained in depth.
