What was the purpose of Das Ganu's 'Ishavasya-Bhavartha-Bodhini' and why did he find the project so unfulfilling despite his efforts?

As explained in Chapter 20 of the Sai Satcharitra, Das Ganu's primary purpose for creating the 'Ishavasya-Bhavartha-Bodhini' was to make the profound wisdom of the Ishavasya Upanishad accessible to those who were ignorant of the Sanskrit language. He intended to compile an explanation of each word in simple Prakrit language using Ovi verses. However, he found the project unfulfilling because the Upanishad is full of deep, hidden meanings. Although he could translate the text word for word, he felt he couldn't grasp the "internal secret." This inability to connect with the core essence of the scripture meant his mind found no joy in the work.