The Humble Triumph of Heraclius in Jerusalem

The Roman Emperor Heraclius is a significant figure in the life of the Prophet ﷺ and the history of the da‘wah in Palestine. The Prophet ﷺ wrote a letter to inviting him to Islam. He was convinced that Islam was the truth and that the Muslims would soon rule in Palestine. So why didn’t he become Muslim? And how did events proceed from there until the Muslim conquest of Palestine just a few years later, under the leadership of Omar ibn al-Khattab (ra)?