There is some deep connection between noability and existence. Even to day, you can even speak about such things because you are a knower... But imagine if the universe were the only universe which you're speaking about, nothing nor nor ever existed. Then who will speak of what? This is why manduk is a little difficult. It makes a very simple statement, but it's something a little disturbing for us.
Swami Sarvapriyananda teaches one of the shortest and most profound upanishads accompanied by Gaudapada's Karika. This lecture covers Mantra 2.