How does Chapter 20 explain the necessity of a Guru for understanding complex scriptures like the Upanishads?

Chapter 20 powerfully illustrates the indispensable role of a Guru in comprehending profound spiritual texts through the story of Das Ganu. The chapter explains that the Upanishads, which contain the very essence of the Vedas, are incredibly difficult to grasp without the grace of both God and a Guru. It asserts that mere scholarship is insufficient, stating that even at the end of an era, a scholar cannot comprehend the hidden truths through their own efforts. The path is described as difficult at every step without a Guru's guidance. However, as Chapter 20 clarifies, for one who is devoted to the Guru's feet, the hidden meanings open up automatically, as this science of Self-knowledge is revealed only to the humble and detached.