Why did Allah not explain His words in the verse (Then indeed, upon Us is its explanation), and can the understanding of scholars reach the level of Allah’s explanation of His verses?

The Quran is clear in its wording and meaning. Any generality found within it has been clarified by the Prophetic Sunnah, which is a revelation from Allah, such as the manner of prayer (Salat) and the amount of Zakat (charity).

There are also verses whose interpretation is known only to Allah, such as the abbreviated letters (al-Huruf al-Muqatta'at). The Companions used to ask the Prophet, peace and blessings be upon him, about the interpretation of verses, as happened with 'Adi ibn Hatim regarding his understanding of the verse about the white and black threads.

People need interpretation for reasons such as misunderstanding, lack of comprehension of the Arabic language, or ignorance of the Sunnah, and not because the Quran is unclear.

The questioner's statement "Do scholars' thoughts reach..." is incorrect, as one does not say "Allah's thought," and no one encompasses Allah's knowledge. Scholars interpret the Quran by referring to the Quran itself, the Sunnah, and the Arabic language. The Quran was revealed in an enduring Arabic language, unlike some previous scriptures that were corrupted by multiple translations.