The Romans
Chapter 30 of the Quran is called, 'The Romans.'
Every Prophet comes with some miracles which prove his divinity. The Beloved Prophet (PBUH)'s miracle was the Quran.
You asked why does Islam begin and end with the Quran - it does not. The Quran is the guiding light of life, a proof of the Beloved Prophet (PBUH)'s divinity, the ladder from earth to heaven, the way to reach Allah, the gold standard of ethics and manners and law, and much more.
In this chapter, Allah talks about The Romans.
30:2 - The Romans have been defeated 30:3 - in a nearby land. Yet following their defeat, they will triumph
(note - this verse was revealed in 614 AD (approx) and the Romans triumphed in 622 AD)
30:4 - within three to nine years. The ˹whole˺ matter rests with Allah before and after ˹victory˺. And on that day the believers will rejoice 30:5 - at the victory willed by Allah. He gives victory to whoever He wills. For He is the Almighty, Most Merciful.
Historically this corresponds to the 602-622 AD war between Persia and the Eastern Romans (Byzantines). In about 614 AD, Khosrow defeated the Romans and pushed them back from present day Iraq-Iran all the way to Constantinople, conquering Palestine, Syria, Egypt and Anatolia. Jerusalem fell. At that point, Jerusalem was ruled by the 'Christian' Romans. It appeared that the Romans were defeated once and for all.
Heraclius, the Emperor of Rome, launched a counterattack from 622 - 626 and invaded the Persian heartland, ultimately leading to the surrender of Persia in 627.
This is the history referenced here in the Quran.
There are many lessons in this for the reader
- A prediction made in the Quran came true years later (within the time frame mentioned - 3 - 9 years, the word in Arabic is Bid'aa Sineen, meaning a time less than 10 years, but more than 3 years)
- Victory and defeat lie in the hands of Allah
- Allah does what He wills even at the scale of Empires