Why did Guru Arjan Dev Ji compile the Adi Granth and what makes it unique among religious scriptures?

Waheguru Ji Ka Khalsa, Waheguru Ji Ki Fateh.

It is a profound blessing to reflect on the monumental contribution of Guru Arjan Dev Ji, the fifth Sikh Guru, who lovingly compiled the Adi Granth in 1604. This sacred scripture was then reverently installed in the newly completed Harmandir Sahib, with the diligent Bhai Gurdas Ji appointed to transcribe its divine verses. The Guru Granth Sahib stands truly unique among the world's religious scriptures. It is a testament to universal spirituality, containing not only the sacred writings of six of the ten Sikh Gurus but also embracing the enlightened compositions of fifteen revered Bhagats from both Hindu and Muslim traditions, including beloved figures like Kabir Ji, Farid Ji, Ravidas Ji, and Namdev Ji. This inclusivity beautifully underscores the Sikh principle of the oneness of humanity and the shared divine experience. Later, Guru Gobind Singh Ji, in an act of eternal wisdom, declared that the Guru Granth Sahib itself would forever be the eternal, living Guru of the Sikhs, guiding and inspiring generations with its timeless wisdom.