Fourth point

Know that the Qur'an has established this firm religion and laid down its foundations and the foundations of the Muslim world.It has also changed communities of mankind and united them in a shared culture and civilization. It hardly needs saying that for something to be established so firmly and extensively requires reinforcement and, therefore, repetition.
Also, in the Qur'an there are answers to the questions asked by many groups of diverse people, of different backgrounds and temperaments and different levels of linguistic ability, understanding and thinking.

Fifth point

Know that the Qur'an mentions many important matters and calls hearts to believe in them, and speaks about subtle truths and invites reason or intellect to have certain knowledge of them. Obviously, in order to secure belief and understanding, reiteration in different styles and contexts is necessary.

Sixth point

The verses of the Qur'an have inward and outward meanings, inward and outward dimensions, and they serve an ultimate purpose for the betterment of mankind, inwardly and outwardly. For example, many legal injunctions and norms of conduct are intended to be derived from some verses, and the relative significance and applicability of injunctions and norms in different contexts require that the verses of the Qur'an should be accordingly reiterated in different ways and contexts. Similarly, in the inward dimensions of meaning, the intellect's effort to understand is challenged and rewarded by verses recurring in different contexts, enabling infinite variety and depth of nuances of meaning.