Why was the Holy Quran not revealed all at once, and why was its revelation preceded by the revelation of the Torah and the Gospel?

All praise is due to Allah, Who possesses ultimate wisdom in managing the affairs of His creation. He decreed that Muhammad (peace be upon him) be the Seal of the Prophets and that the Holy Quran be revealed to him, as stated in the Hadith: "Indeed, I am, with Allah in the Mother of the Book, the Seal of the Prophets, while Adam (peace be upon him) was still kneaded in his clay." Scholars have mentioned that humanity passed through stages of development until it reached maturity. Thus, it was fitting that the final message be revealed during this period of humanity's maturity, while the previous messages were suitable for their respective times.